--- rfc1738.txt	2003-10-12 10:47:23.000000000 +0900
+++ rfc2396.txt	2003-10-12 10:44:55.000000000 +0900
@@ -1,14 +1,12 @@
 Network Working Group                                     T. Berners-Lee
-Request for Comments: 1738                                          CERN
+Request for Comments: 2396                                       MIT/LCS
+Updates: 1808, 1738                                          R. Fielding
+Category: Standards Track                                    U.C. Irvine
-Category: Standards Track                                    L. Masinter
+                                                             L. Masinter
                                                        Xerox Corporation
-                                                             M. McCahill
-                                                 University of Minnesota
-                                                                 Editors
-                                                           December 1994
+                                                             August 1998
!Network Working Group                                        R. Fielding
!Request for Comments: 1808                                     UC Irvine
!Category: Standards Track                                      June 1995
 
-
-                    Uniform Resource Locators (URL)
!                   Relative Uniform Resource Locators
+           Uniform Resource Identifiers (URI): Generic Syntax
 
 Status of this Memo
 
@@ -18,1107 +16,1677 @@
    Official Protocol Standards" (STD 1) for the standardization state
    and status of this protocol.  Distribution of this memo is unlimited.
 
+Copyright Notice

+   Copyright (C) The Internet Society (1998).  All Rights Reserved.

+IESG Note

+   This paper describes a "superset" of operations that can be applied
+   to URI.  It consists of both a grammar and a description of basic
+   functionality for URI.  To understand what is a valid URI, both the
+   grammar and the associated description have to be studied.  Some of
+   the functionality described is not applicable to all URI schemes, and
+   some operations are only possible when certain media types are
+   retrieved using the URI, regardless of the scheme used.

Abstract
 
-   This document specifies a Uniform Resource Locator (URL), the syntax
-   and semantics of formalized information for location and access of
-   resources via the Internet.

!   A Uniform Resource Locator (URL) is a compact representation of the
!   location and access method for a resource available via the Internet.
+   A Uniform Resource Identifier (URI) is a compact string of characters
+   for identifying an abstract or physical resource.
!   When embedded within a base document, a URL in its absolute form may
!   contain a great deal of information which is already known from the
!   context of that base document's retrieval, including the scheme,
!   network location, and parts of the url-path.  In situations where the
!   base URL is well-defined and known to the parser (human or machine),
!   it is useful to be able to embed URL references which inherit that
!   context rather than re-specifying it in every instance.
!    This document defines the syntax and semantics for such Relative Uniform
!   Resource Locators.
+    This document defines the generic syntax of URI, including both absolute and
+   relative forms, and guidelines for their use; it revises and replaces
+   the generic definitions in RFC 1738 and RFC 1808.

+   This document defines a grammar that is a superset of all valid URI,
+   such that an implementation can parse the common components of a URI
+   reference without knowing the scheme-specific requirements of every
+   possible identifier type.  This document does not define a generative
+   grammar for URI; that task will be performed by the individual
+   specifications of each URI scheme.
 
1. Introduction

-   This document describes the syntax and semantics for a compact string
-   representation for a resource available via the Internet.  These
-   strings are called "Uniform Resource Locators" (URLs).
-
+   Uniform Resource Identifiers (URI) provide a simple and extensible
+   means for identifying a resource.  This specification of URI syntax and semantics
-   The specification 
is derived from concepts introduced by the
-   World-Wide
+   World Wide
Web global information initiative, whose use of such objects
dates from 1990 and is described in "Universal Resource Identifiers in WWW"
-  , RFC 1630. The specification of URLs
+   [RFC1630].  The specification of URI
is designed to meet the 
-   requirements
+   recommendations
laid out in "Functional 
-   Requirements 
+   Recommendations
for Internet Resource Locators"
-[12].
+[RFC1736] and "Functional Requirements for Uniform Resource Names" [RFC1737].

+   This document updates and merges "Uniform Resource Locators"
+   [RFC1738] and "Relative Uniform Resource Locators" [RFC1808] in order
+   to define a single, generic syntax for all URI.  It excludes those
+   portions of RFC 1738 that defined the specific syntax of individual
+   URL schemes; those portions will be updated as separate documents, as
+   will the process for registration of new URI schemes.  This document
+   does not discuss the issues and recommendation for dealing with
+   characters outside of the US-ASCII character set [ASCII]; those
+   recommendations are discussed in a separate document.
+
+   All significant changes from the prior RFCs are noted in Appendix G.

-   This document was written by the URI working group of the Internet
-   Engineering Task Force.  Comments may be addressed to the editors, or
-   to the URI-WG <uri@bunyip.com>. Discussions of the group are archived
-   at <URL:http://www.acl.lanl.gov/URI/archive/uri-archive.index.html>
 
!1.  Introduction
!
!   This document describes the syntax and semantics for "relative"
!   Uniform Resource Locators (relative URLs): a compact representation
!   of the location of a resource relative to an absolute base URL.  It
!   is a companion to RFC 1738, "Uniform Resource Locators (URL)" [2],
!   which specifies the syntax and semantics of absolute URLs.
!
!   A common use for Uniform Resource Locators is to embed them within a
!   document (referred to as the "base" document) for the purpose of
!   identifying other Internet-accessible resources.  For example, in
!   hypertext documents, URLs can be used as the identifiers for
!   hypertext link destinations.
!
!   Absolute URLs contain a great deal of information which may already
!   be known from the context of the base document's retrieval, including
!   the scheme, network location, and parts of the URL path.  In
!   situations where the base URL is well-defined and known, it is useful
!   to be able to embed a URL reference which inherits that context
!   rather than re-specifying it within each instance.  Relative URLs can
!   also be used within data-entry dialogs to decrease the number of
!   characters necessary to describe a location.
!
!   In addition, it is often the case that a group or "tree" of documents
!   has been constructed to serve a common purpose; the vast majority of
!   URLs in these documents point to locations within the tree rather
!   than outside of it.  Similarly, documents located at a particular
!   Internet site are much more likely to refer to other resources at
!   that site than to resources at remote sites.
!
!   Relative addressing of URLs allows document trees to be partially
!   independent of their location and access scheme.  For instance, it is
!   possible for a single set of hypertext documents to be simultaneously
!   accessible and traversable via each of the "file", "http", and "ftp"
!   schemes if the documents refer to each other using relative URLs.
!   Furthermore, document trees can be moved, as a whole, without
!   changing any of the embedded URLs.  Experience within the World-Wide
!   Web has demonstrated that the ability to perform relative referencing
!   is necessary for the long-term usability of embedded URLs.

+1.1 Overview of URI
+
+   URI are characterized by the following definitions:
+
+      Uniform
+         Uniformity provides several benefits: it allows different types
+         of resource identifiers to be used in the same context, even
+         when the mechanisms used to access those resources may differ;
+         it allows uniform semantic interpretation of common syntactic
+         conventions across different types of resource identifiers; it
+         allows introduction of new types of resource identifiers
+         without interfering with the way that existing identifiers are
+         used; and, it allows the identifiers to be reused in many
+         different contexts, thus permitting new applications or
+         protocols to leverage a pre-existing, large, and widely-used
+         set of resource identifiers.
+
+      Resource
+         A resource can be anything that has identity.  Familiar
+         examples include an electronic document, an image, a service
+         (e.g., "today's weather report for Los Angeles"), and a
+         collection of other resources.  Not all resources are network
+         "retrievable"; e.g., human beings, corporations, and bound
+         books in a library can also be considered resources.
+
+         The resource is the conceptual mapping to an entity or set of
+         entities, not necessarily the entity which corresponds to that
+         mapping at any particular instance in time.  Thus, a resource
+         can remain constant even when its content---the entities to
+         which it currently corresponds---changes over time, provided
+         that the conceptual mapping is not changed in the process.
+
+      Identifier
+         An identifier is an object that can act as a reference to
+         something that has identity.  In the case of URI, the object is
+         a sequence of characters with a restricted syntax.
+
+   Having identified a resource, a system may perform a variety of
+   operations on the resource, as might be characterized by such words
+   as `access', `update', `replace', or `find attributes'.
+
+1.2. URI, URL, and URN
+
+   A URI can be further classified as a locator, a name, or both.  The
+   term "Uniform Resource Locator" (URL) refers to the subset of URI
+   that identify resources via a representation of their primary access
+   mechanism (e.g., their network "location"), rather than identifying
+   the resource by name or by some other attribute(s) of that resource.
+   The term "Uniform Resource Name" (URN) refers to the subset of URI
+   that are required to remain globally unique and persistent even when
+   the resource ceases to exist or becomes unavailable.
+
+   The URI scheme (Section 3.1) defines the namespace of the URI, and
+   thus may further restrict the syntax and semantics of identifiers
+   using that scheme.  This specification defines those elements of the
+   URI syntax that are either required of all URI schemes or are common
+   to many URI schemes.  It thus defines the syntax and semantics that
+   are needed to implement a scheme-independent parsing mechanism for
+   URI references, such that the scheme-dependent handling of a URI can
+   be postponed until the scheme-dependent semantics are needed.  We use
+   the term URL below when describing syntax or semantics that only
+   apply to locators.
+
+   Although many URL schemes are named after protocols, this does not
+   imply that the only way to access the URL's resource is via the named
+   protocol.  Gateways, proxies, caches, and name resolution services
+   might be used to access some resources, independent of the protocol
+   of their origin, and the resolution of some URL may require the use
+   of more than one protocol (e.g., both DNS and HTTP are typically used
+   to access an "http" URL's resource when it can't be found in a local
+   cache).
+
+   A URN differs from a URL in that it's primary purpose is persistent
+   labeling of a resource with an identifier.  That identifier is drawn
+   from one of a set of defined namespaces, each of which has its own
+   set name structure and assignment procedures.  The "urn" scheme has
+   been reserved to establish the requirements for a standardized URN
+   namespace, as defined in "URN Syntax" [RFC2141] and its related
+   specifications.
+
+   Most of the examples in this specification demonstrate URL, since
+   they allow the most varied use of the syntax and often have a
+   hierarchical namespace.  A parser of the URI syntax is capable of
+   parsing both URL and URN references as a generic URI; once the scheme
+   is determined, the scheme-specific parsing can be performed on the
+   generic URI components.  In other words, the URI syntax is a superset
+   of the syntax of all URI schemes.
+
+1.3. Example URI
+
+   The following examples illustrate URI that are in common use.
+
+   ftp://ftp.is.co.za/rfc/rfc1808.txt
+      -- ftp scheme for File Transfer Protocol services
+
+   gopher://spinaltap.micro.umn.edu/00/Weather/California/Los%20Angeles
+      -- gopher scheme for Gopher and Gopher+ Protocol services
+
+   http://www.math.uio.no/faq/compression-faq/part1.html
+      -- http scheme for Hypertext Transfer Protocol services
+
+   mailto:mduerst@ifi.unizh.ch
+      -- mailto scheme for electronic mail addresses
+
+   news:comp.infosystems.www.servers.unix
+      -- news scheme for USENET news groups and articles
+
+   telnet://melvyl.ucop.edu/
+      -- telnet scheme for interactive services via the TELNET Protocol
+
+1.4. Hierarchical URI and Relative Forms
+
+   An absolute identifier refers to a resource independent of the
+   context in which the identifier is used.  In contrast, a relative
+   identifier refers to a resource by describing the difference within a
+   hierarchical namespace between the current context and an absolute
+   identifier of the resource.
+
+   Some URI schemes support a hierarchical naming system, where the
+   hierarchy of the name is denoted by a "/" delimiter separating the
+   components in the scheme. This document defines a scheme-independent
+   `relative' form of URI reference that can be used in conjunction with
+   a `base' URI (of a hierarchical scheme) to produce another URI. The
+   syntax of hierarchical URI is described in Section 3; the relative
+   URI calculation is described in Section 5.
+
+1.5. URI Transcribability
+
+   The URI syntax was designed with global transcribability as one of
+   its main concerns. A URI is a sequence of characters from a very
+   limited set, i.e. the letters of the basic Latin alphabet, digits,
+   and a few special characters.  A URI may be represented in a variety
+   of ways: e.g., ink on paper, pixels on a screen, or a sequence of
+   octets in a coded character set.  The interpretation of a URI depends
+   only on the characters used and not how those characters are
+   represented in a network protocol.
+
+   The goal of transcribability can be described by a simple scenario.
+   Imagine two colleagues, Sam and Kim, sitting in a pub at an
+   international conference and exchanging research ideas.  Sam asks Kim
+   for a location to get more information, so Kim writes the URI for the
+   research site on a napkin.  Upon returning home, Sam takes out the
+   napkin and types the URI into a computer, which then retrieves the
+   information to which Kim referred.
+
+   There are several design concerns revealed by the scenario:
+
+      o  A URI is a sequence of characters, which is not always
+         represented as a sequence of octets.
+
+      o  A URI may be transcribed from a non-network source, and thus
+         should consist of characters that are most likely to be able to
+         be typed into a computer, within the constraints imposed by
+         keyboards (and related input devices) across languages and
+         locales.
+
+      o  A URI often needs to be remembered by people, and it is easier
+         for people to remember a URI when it consists of meaningful
+         components.
+
+   These design concerns are not always in alignment.  For example, it
+   is often the case that the most meaningful name for a URI component
+   would require characters that cannot be typed into some systems.  The
+   ability to transcribe the resource identifier from one medium to
+   another was considered more important than having its URI consist of
+   the most meaningful of components.  In local and regional contexts
+   and with improving technology, users might benefit from being able to
+   use a wider range of characters; such use is not defined in this
+   document.

-2. General URL Syntax
 
-   Just as there are many different methods of access to resources,
-   there are several schemes for describing the location of such
-   resources.
+
 
-   The generic syntax for URLs provides a framework for new schemes to
-   be established using protocols other than those defined in this
-   document.
 
-   URLs are used to `locate' resources, by providing an abstract
-   identification of the resource location.  Having located a resource,
-   a system may perform a variety of operations on the resource, as
-   might be characterized by such words as `access', `update',
-   `replace', `find attributes'. In general, only the `access' method
-   needs to be specified for any URL scheme.

-3. Specific Schemes
!2.3.  Specific Schemes and their Syntactic Categories
-
-   The mapping for some existing standard and experimental protocols is
-   outlined in the BNF syntax definition.  Notes on particular protocols
-   follow. The schemes covered are:
-
-   ftp                     File Transfer protocol
-   http                    Hypertext Transfer Protocol
-   gopher                  The Gopher protocol
-   mailto                  Electronic mail address
-   news                    USENET news
-   nntp                    USENET news using NNTP access
-   telnet                  Reference to interactive sessions
-   wais                    Wide Area Information Servers
-   file                    Host-specific file names
-   prospero                Prospero Directory Service
-
-   Other schemes may be specified by future specifications. Section 4 of
-   this document describes how new schemes may be registered, and lists
-   some scheme names that are under development.

!   Each URL scheme has its own rules regarding the presence or absence
!   of the syntactic components described in Sections 2.1 and 2.2.  In
!   addition, some schemes are never appropriate for use with relative
!   URLs.  However, since relative URLs will only be used within contexts
!   in which they are useful, these scheme-specific differences can be
!   ignored by the resolution process.
!
!   Within this section, we include as examples only those schemes that
!   have a defined URL syntax in RFC 1738 [2].  The following schemes are
!   never used with relative URLs:
!
!      mailto     Electronic Mail
!      news       USENET news
!      telnet     TELNET Protocol for Interactive Sessions
!
!   Some URL schemes allow the use of reserved characters for purposes
!   outside the generic-RL syntax given above.  However, such use is
!   rare.  Relative URLs can be used with these schemes whenever the
!   applicable base URL follows the generic-RL syntax.
!
!      gopher     Gopher and Gopher+ Protocols
!      prospero   Prospero Directory Service
!      wais       Wide Area Information Servers Protocol
!
!   Users of gopher URLs should note that gopher-type information is
!   almost always included at the beginning of what would be the
!   generic-RL path.  If present, this type information prevents
!   relative-path references to documents with differing gopher-types.
!
!   Finally, the following schemes can always be parsed using the
!   generic-RL syntax.  This does not necessarily imply that relative
!   URLs will be useful with these schemes -- that decision is left to
!   the system implementation and the author of the base document.
!
!      file       Host-specific Files
!      ftp        File Transfer Protocol
!      http       Hypertext Transfer Protocol
!      nntp       USENET news using NNTP access
!
!   NOTE: Section 5 of RFC 1738 specifies that the question-mark
!         character ("?") is allowed in an ftp or file path segment.
!         However, this is not true in practice and is believed to be an
!         error in the RFC.  Similarly, RFC 1738 allows the reserved
!         character semicolon (";") within an http path segment, but does
!         not define its semantics; the correct semantics are as defined
!         by this document for <params>.
!
!   We recommend that new schemes be designed to be parsable via the
!   generic-RL syntax if they are intended to be used with relative URLs.
!   A description of the allowed relative forms should be included when a
!   new scheme is registered, as per Section 4 of RFC 1738 [2].
-
-3.2. FTP
-
-   The FTP URL scheme is used to designate files and directories on
-   Internet hosts accessible using the FTP protocol (RFC959).
-
-   A FTP URL follow the syntax described in Section 3.1.  If :<port> is
-   omitted, the port defaults to 21.
-
-3.2.1. FTP Name and Password
-
-   A user name and password may be supplied; they are used in the ftp
-   "USER" and "PASS" commands after first making the connection to the
-   FTP server.  If no user name or password is supplied and one is
-   requested by the FTP server, the conventions for "anonymous" FTP are
-   to be used, as follows:
-
-        The user name "anonymous" is supplied.
-
-        The password is supplied as the Internet e-mail address
-        of the end user accessing the resource.
-
-   If the URL supplies a user name but no password, and the remote
-   server requests a password, the program interpreting the FTP URL
-   should request one from the user.
-
-3.2.2. FTP url-path
-
-   The url-path of a FTP URL has the following syntax:
-
-        <cwd1>/<cwd2>/.../<cwdN>/<name>;type=<typecode>
-
-   Where <cwd1> through <cwdN> and <name> are (possibly encoded) strings
-   and <typecode> is one of the characters "a", "i", or "d".  The part
-   ";type=<typecode>" may be omitted. The <cwdx> and <name> parts may be
-   empty. The whole url-path may be omitted, including the "/"
-   delimiting it from the prefix containing user, password, host, and
-   port.
-
-   The url-path is interpreted as a series of FTP commands as follows:
-
-      Each of the <cwd> elements is to be supplied, sequentially, as the
-      argument to a CWD (change working directory) command.
-
-      If the typecode is "d", perform a NLST (name list) command with
-      <name> as the argument, and interpret the results as a file
-      directory listing.
-
-      Otherwise, perform a TYPE command with <typecode> as the argument,
-      and then access the file whose name is <name> (for example, using
-      the RETR command.)
-
-   Within a name or CWD component, the characters "/" and ";" are
-   reserved and must be encoded. The components are decoded prior to
-   their use in the FTP protocol.  In particular, if the appropriate FTP
-   sequence to access a particular file requires supplying a string
-   containing a "/" as an argument to a CWD or RETR command, it is
-   necessary to encode each "/".
-
-   For example, the URL <URL:ftp://myname@host.dom/%2Fetc/motd> is
-   interpreted by FTP-ing to "host.dom", logging in as "myname"
-   (prompting for a password if it is asked for), and then executing
-   "CWD /etc" and then "RETR motd". This has a different meaning from
-   <URL:ftp://myname@host.dom/etc/motd> which would "CWD etc" and then
-   "RETR motd"; the initial "CWD" might be executed relative to the
-   default directory for "myname". On the other hand,
-   <URL:ftp://myname@host.dom//etc/motd>, would "CWD " with a null
-   argument, then "CWD etc", and then "RETR motd".
-
-   FTP URLs may also be used for other operations; for example, it is
-   possible to update a file on a remote file server, or infer
-   information about it from the directory listings. The mechanism for
-   doing so is not spelled out here.
-
-3.2.3. FTP Typecode is Optional
-
-   The entire ;type=<typecode> part of a FTP URL is optional. If it is
-   omitted, the client program interpreting the URL must guess the
-   appropriate mode to use. In general, the data content type of a file
-   can only be guessed from the name, e.g., from the suffix of the name;
-   the appropriate type code to be used for transfer of the file can
-   then be deduced from the data content of the file.
-
-
-3.2.5. Optimization
-
-   Clients accessing resources via FTP may employ additional heuristics
-   to optimize the interaction. For some FTP servers, for example, it
-   may be reasonable to keep the control connection open while accessing
-   multiple URLs from the same server. However, there is no common
-   hierarchical model to the FTP protocol, so if a directory change
-   command has been given, it is impossible in general to deduce what
-   sequence should be given to navigate to another directory for a
-   second retrieval, if the paths are different.  The only reliable
-   algorithm is to disconnect and reestablish the control connection.
-
-3.3. HTTP
-
-   The HTTP URL scheme is used to designate Internet resources
-   accessible using HTTP (HyperText Transfer Protocol).
-
-   The HTTP protocol is specified elsewhere. This specification only
-   describes the syntax of HTTP URLs.
-
-   An HTTP URL takes the form:
-
-      http://<host>:<port>/<path>?<searchpart>
-
-   where <host> and <port> are as described in Section 3.1. If :<port>
-   is omitted, the port defaults to 80.  No user name or password is
-   allowed.  <path> is an HTTP selector, and <searchpart> is a query
-   string. The <path> is optional, as is the <searchpart> and its
-   preceding "?". If neither <path> nor <searchpart> is present, the "/"
-   may also be omitted.
-
-   Within the <path> and <searchpart> components, "/", ";", "?" are
-   reserved.  The "/" character may be used within HTTP to designate a
-   hierarchical structure.
-
-3.4. GOPHER
-
-   The Gopher URL scheme is used to designate Internet resources
-   accessible using the Gopher protocol.
-
-   The base Gopher protocol is described in RFC 1436 and supports items
-   and collections of items (directories). The Gopher+ protocol is a set
-   of upward compatible extensions to the base Gopher protocol and is
-   described in [2]. Gopher+ supports associating arbitrary sets of
-   attributes and alternate data representations with Gopher items.
-   Gopher URLs accommodate both Gopher and Gopher+ items and item
-   attributes.
-
-3.4.1. Gopher URL syntax
-
-   A Gopher URL takes the form:
-
-      gopher://<host>:<port>/<gopher-path>
-
-   where <gopher-path> is one of
-
-       <gophertype><selector>
-       <gophertype><selector>%09<search>
-       <gophertype><selector>%09<search>%09<gopher+_string>
-
-   If :<port> is omitted, the port defaults to 70.  <gophertype> is a
-   single-character field to denote the Gopher type of the resource to
-   which the URL refers. The entire <gopher-path> may also be empty, in
-   which case the delimiting "/" is also optional and the <gophertype>
-   defaults to "1".
-
-   <selector> is the Gopher selector string.  In the Gopher protocol,
-   Gopher selector strings are a sequence of octets which may contain
-   any octets except 09 hexadecimal (US-ASCII HT or tab) 0A hexadecimal
-   (US-ASCII character LF), and 0D (US-ASCII character CR).
-
-   Gopher clients specify which item to retrieve by sending the Gopher
-   selector string to a Gopher server.
-
-   Within the <gopher-path>, no characters are reserved.
-
-   Note that some Gopher <selector> strings begin with a copy of the
-   <gophertype> character, in which case that character will occur twice
-   consecutively. The Gopher selector string may be an empty string;
-   this is how Gopher clients refer to the top-level directory on a
-   Gopher server.
-
-3.4.2 Specifying URLs for Gopher Search Engines
-
-   If the URL refers to a search to be submitted to a Gopher search
-   engine, the selector is followed by an encoded tab (%09) and the
-   search string. To submit a search to a Gopher search engine, the
-   Gopher client sends the <selector> string (after decoding), a tab,
-   and the search string to the Gopher server.
-
-3.4.3 URL syntax for Gopher+ items
-
-   URLs for Gopher+ items have a second encoded tab (%09) and a Gopher+
-   string. Note that in this case, the %09<search> string must be
-   supplied, although the <search> element may be the empty string.
-
-   The <gopher+_string> is used to represent information required for
-   retrieval of the Gopher+ item. Gopher+ items may have alternate
-   views, arbitrary sets of attributes, and may have electronic forms
-   associated with them.
-
-   To retrieve the data associated with a Gopher+ URL, a client will
-   connect to the server and send the Gopher selector, followed by a tab
-   and the search string (which may be empty), followed by a tab and the
-   Gopher+ commands.
-
-3.4.4 Default Gopher+ data representation
-
-   When a Gopher server returns a directory listing to a client, the
-   Gopher+ items are tagged with either a "+" (denoting Gopher+ items)
-   or a "?" (denoting Gopher+ items which have a +ASK form associated
-   with them). A Gopher URL with a Gopher+ string consisting of only a
-   "+" refers to the default view (data representation) of the item
-   while a Gopher+ string containing only a "?" refer to an item with a
-   Gopher electronic form associated with it.
-
-3.4.5 Gopher+ items with electronic forms
-
-   Gopher+ items which have a +ASK associated with them (i.e. Gopher+
-   items tagged with a "?") require the client to fetch the item's +ASK
-   attribute to get the form definition, and then ask the user to fill
-   out the form and return the user's responses along with the selector
-   string to retrieve the item.  Gopher+ clients know how to do this but
-   depend on the "?" tag in the Gopher+ item description to know when to
-   handle this case. The "?" is used in the Gopher+ string to be
-   consistent with Gopher+ protocol's use of this symbol.
-
-3.4.6 Gopher+ item attribute collections
-
-   To refer to the Gopher+ attributes of an item, the Gopher URL's
-   Gopher+ string consists of "!" or "$". "!" refers to the all of a
-   Gopher+ item's attributes. "$" refers to all the item attributes for
-   all items in a Gopher directory.
-
-3.4.7 Referring to specific Gopher+ attributes
-
-   To refer to specific attributes, the URL's gopher+_string is
-   "!<attribute_name>" or "$<attribute_name>". For example, to refer to
-   the attribute containing the abstract of an item, the gopher+_string
-   would be "!+ABSTRACT".
-
-   To refer to several attributes, the gopher+_string consists of the
-   attribute names separated by coded spaces. For example,
-   "!+ABSTRACT%20+SMELL" refers to the +ABSTRACT and +SMELL attributes
-   of an item.
-
-3.4.8 URL syntax for Gopher+ alternate views
-
-   Gopher+ allows for optional alternate data representations (alternate
-   views) of items. To retrieve a Gopher+ alternate view, a Gopher+
-   client sends the appropriate view and language identifier (found in
-   the item's +VIEW attribute). To refer to a specific Gopher+ alternate
-   view, the URL's Gopher+ string would be in the form:
-
-        +<view_name>%20<language_name>
-
-   For example, a Gopher+ string of "+application/postscript%20Es_ES"
-   refers to the Spanish language postscript alternate view of a Gopher+
-   item.
-
-3.4.9 URL syntax for Gopher+ electronic forms
-
-   The gopher+_string for a URL that refers to an item referenced by a
-   Gopher+ electronic form (an ASK block) filled out with specific
-   values is a coded version of what the client sends to the server.
-   The gopher+_string is of the form:
-
-+%091%0D%0A+-1%0D%0A<ask_item1_value>%0D%0A<ask_item2_value>%0D%0A.%0D%0A
-
-   To retrieve this item, the Gopher client sends:
-
-       <a_gopher_selector><tab>+<tab>1<cr><lf>
-       +-1<cr><lf>
-       <ask_item1_value><cr><lf>
-       <ask_item2_value><cr><lf>
-       .<cr><lf>
-
-   to the Gopher server.
-
-3.5. MAILTO
-
-   The mailto URL scheme is used to designate the Internet mailing
-   address of an individual or service. No additional information other
-   than an Internet mailing address is present or implied.
-
-   A mailto URL takes the form:
-
-        mailto:<rfc822-addr-spec>
-
-   where <rfc822-addr-spec> is (the encoding of an) addr-spec, as
-   specified in RFC 822 [6]. Within mailto URLs, there are no reserved
-   characters.
-
-   Note that the percent sign ("%") is commonly used within RFC 822
-   addresses and must be encoded.
-
-   Unlike many URLs, the mailto scheme does not represent a data object
-   to be accessed directly; there is no sense in which it designates an
-   object. It has a different use than the message/external-body type in
-   MIME.
-
-3.6. NEWS
-
-   The news URL scheme is used to refer to either news groups or
-   individual articles of USENET news, as specified in RFC 1036.
-
-   A news URL takes one of two forms:
-
-     news:<newsgroup-name>
-     news:<message-id>
-
-   A <newsgroup-name> is a period-delimited hierarchical name, such as
-   "comp.infosystems.www.misc". A <message-id> corresponds to the
-   Message-ID of section 2.1.5 of RFC 1036, without the enclosing "<"
-   and ">"; it takes the form <unique>@<full_domain_name>.  A message
-   identifier may be distinguished from a news group name by the
-   presence of the commercial at "@" character. No additional characters
-   are reserved within the components of a news URL.
-
-   If <newsgroup-name> is "*" (as in <URL:news:*>), it is used to refer
-   to "all available news groups".
-
-   The news URLs are unusual in that by themselves, they do not contain
-   sufficient information to locate a single resource, but, rather, are
-   location-independent.
-
-3.7. NNTP
-
-   The nntp URL scheme is an alternative method of referencing news
-   articles, useful for specifying news articles from NNTP servers (RFC
-   977).
-
-   A nntp URL take the form:
-
-      nntp://<host>:<port>/<newsgroup-name>/<article-number>
-
-   where <host> and <port> are as described in Section 3.1. If :<port>
-   is omitted, the port defaults to 119.
-
-   The <newsgroup-name> is the name of the group, while the <article-
-   number> is the numeric id of the article within that newsgroup.
-
-   Note that while nntp: URLs specify a unique location for the article
-   resource, most NNTP servers currently on the Internet today are
-   configured only to allow access from local clients, and thus nntp
-   URLs do not designate globally accessible resources. Thus, the news:
-   form of URL is preferred as a way of identifying news articles.
-
-3.8. TELNET
-
-   The Telnet URL scheme is used to designate interactive services that
-   may be accessed by the Telnet protocol.
-
-   A telnet URL takes the form:
-
-       telnet://<user>:<password>@<host>:<port>/
-
-   as specified in Section 3.1. The final "/" character may be omitted.
-   If :<port> is omitted, the port defaults to 23.  The :<password> can
-   be omitted, as well as the whole <user>:<password> part.
-
-   This URL does not designate a data object, but rather an interactive
-   service. Remote interactive services vary widely in the means by
-   which they allow remote logins; in practice, the <user> and
-   <password> supplied are advisory only: clients accessing a telnet URL
-   merely advise the user of the suggested username and password.
-
-3.9.  WAIS
-
-   The WAIS URL scheme is used to designate WAIS databases, searches, or
-   individual documents available from a WAIS database. WAIS is
-   described in [7]. The WAIS protocol is described in RFC 1625 [17];
-   Although the WAIS protocol is based on Z39.50-1988, the WAIS URL
-   scheme is not intended for use with arbitrary Z39.50 services.
-
-   A WAIS URL takes one of the following forms:
-
-     wais://<host>:<port>/<database>
-     wais://<host>:<port>/<database>?<search>
-     wais://<host>:<port>/<database>/<wtype>/<wpath>
-
-   where <host> and <port> are as described in Section 3.1. If :<port>
-   is omitted, the port defaults to 210.  The first form designates a
-   WAIS database that is available for searching. The second form
-   designates a particular search.  <database> is the name of the WAIS
-   database being queried.
-
-   The third form designates a particular document within a WAIS
-   database to be retrieved. In this form <wtype> is the WAIS
-   designation of the type of the object. Many WAIS implementations
-   require that a client know the "type" of an object prior to
-   retrieval, the type being returned along with the internal object
-   identifier in the search response.  The <wtype> is included in the
-   URL in order to allow the client interpreting the URL adequate
-   information to actually retrieve the document.
-
-   The <wpath> of a WAIS URL consists of the WAIS document-id, encoded
-   as necessary using the method described in Section 2.2. The WAIS
-   document-id should be treated opaquely; it may only be decomposed by
-   the server that issued it.
-
-3.10 FILES
-
-   The file URL scheme is used to designate files accessible on a
-   particular host computer. This scheme, unlike most other URL schemes,
-   does not designate a resource that is universally accessible over the
-   Internet.
-
-   A file URL takes the form:
-
-       file://<host>/<path>
-
-   where <host> is the fully qualified domain name of the system on
-   which the <path> is accessible, and <path> is a hierarchical
-   directory path of the form <directory>/<directory>/.../<name>.
-
-   For example, a VMS file
-
-     DISK$USER:[MY.NOTES]NOTE123456.TXT
-
-   might become
-
-     <URL:file://vms.host.edu/disk$user/my/notes/note12345.txt>
-
-   As a special case, <host> can be the string "localhost" or the empty
-   string; this is interpreted as `the machine from which the URL is
-   being interpreted'.
-
-   The file URL scheme is unusual in that it does not specify an
-   Internet protocol or access method for such files; as such, its
-   utility in network protocols between hosts is limited.
-
-3.11 PROSPERO
-
-   The Prospero URL scheme is used to designate resources that are
-   accessed via the Prospero Directory Service. The Prospero protocol is
-   described elsewhere [14].
-
-   A prospero URLs takes the form:
-
-      prospero://<host>:<port>/<hsoname>;<field>=<value>
-
-   where <host> and <port> are as described in Section 3.1. If :<port>
-   is omitted, the port defaults to 1525. No username or password is
-   allowed.
-
-   The <hsoname> is the host-specific object name in the Prospero
-   protocol, suitably encoded.  This name is opaque and interpreted by
-   the Prospero server.  The semicolon ";" is reserved and may not
-   appear without quoting in the <hsoname>.
-
-   Prospero URLs are interpreted by contacting a Prospero directory
-   server on the specified host and port to determine appropriate access
-   methods for a resource, which might themselves be represented as
-   different URLs. External Prospero links are represented as URLs of
-   the underlying access method and are not represented as Prospero
-   URLs.
-
-   Note that a slash "/" may appear in the <hsoname> without quoting and
-   no significance may be assumed by the application.  Though slashes
-   may indicate hierarchical structure on the server, such structure is
-   not guaranteed. Note that many <hsoname>s begin with a slash, in
-   which case the host or port will be followed by a double slash: the
-   slash from the URL syntax, followed by the initial slash from the
-   <hsoname>. (E.g., <URL:prospero://host.dom//pros/name> designates a
-   <hsoname> of "/pros/name".)
-
-   In addition, after the <hsoname>, optional fields and values
-   associated with a Prospero link may be specified as part of the URL.
-   When present, each field/value pair is separated from each other and
-   from the rest of the URL by a ";" (semicolon).  The name of the field
-   and its value are separated by a "=" (equal sign). If present, these
-   fields serve to identify the target of the URL.  For example, the
-   OBJECT-VERSION field can be specified to identify a specific version
-   of an object.
-
-4. REGISTRATION OF NEW SCHEMES
-
-   A new scheme may be introduced by defining a mapping onto a
-   conforming URL syntax, using a new prefix. URLs for experimental
-   schemes may be used by mutual agreement between parties. Scheme names
-   starting with the characters "x-" are reserved for experimental
-   purposes.
-
-   The Internet Assigned Numbers Authority (IANA) will maintain a
-   registry of URL schemes. Any submission of a new URL scheme must
-   include a definition of an algorithm for accessing of resources
-   within that scheme and the syntax for representing such a scheme.
-
-   URL schemes must have demonstrable utility and operability.  One way
-   to provide such a demonstration is via a gateway which provides
-   objects in the new scheme for clients using an existing protocol.  If
-   the new scheme does not locate resources that are data objects, the
-   properties of names in the new space must be clearly defined.
-
-   New schemes should try to follow the same syntactic conventions of
-   existing schemes, where appropriate.  It is likewise recommended
-   that, where a protocol allows for retrieval by URL, that the client
-   software have provision for being configured to use specific gateway
-   locators for indirect access through new naming schemes.
-
-   The following scheme have been proposed at various times, but this
-   document does not define their syntax or use at this time. It is
-   suggested that IANA reserve their scheme names for future definition:
-
-   afs              Andrew File System global file names.
-   mid              Message identifiers for electronic mail.
-   cid              Content identifiers for MIME body parts.
-   nfs              Network File System (NFS) file names.
-   tn3270           Interactive 3270 emulation sessions.
-   mailserver       Access to data available from mail servers.
-   z39.50           Access to ANSI Z39.50 services.
-
-5. BNF for specific URL schemes
!2.2.  BNF for Relative URLs
+1.6. Syntax Notation and Common Elements
+
+   This document uses two conventions to describe and define the syntax
+   for URI.  The first, called the layout form, is a general description
+   of the order of components and component separators, as in
+
+      <first>/<second>;<third>?<fourth>
+
+   The component names are enclosed in angle-brackets and any characters
+   outside angle-brackets are literal separators.  Whitespace should be
+   ignored.  These descriptions are used informally and do not define
+   the syntax requirements.
-
-   This is a BNF-like description of the Uniform Resource Locator
!   This is a BNF-like description of the Relative Uniform Resource Locator
+   The second convention is a BNF-like grammar, used to define the formal URI
-   syntax, using the conventions of RFC822,
!   syntax, using the conventions of RFC 822 [5],
+   syntax.  The grammar is that of [RFC822],
-!+ except that "|" is used to designate alternatives. 
-   , and brackets [] are used around optional or repeated elements. 
-  Briefly,
!   Briefly,
+   Briefly, rules are separated from
+   definitions by an equal "=", indentation is used to continue a rule
+   definition over more than one line,
-!+ literals are quoted with "",
!+   parentheses "(" and ")" are used to group elements,
-!   optional elements are enclosed in [brackets],
+  optional elements  are enclosed in "[" and "]" brackets,
-!+ and elements may be preceded with <n>* to designate n or more repetitions of the -!+ following element; n defaults to 0.
 
+   Unlike many specifications that use a BNF-like grammar to define the
+   bytes (octets) allowed by a protocol, the URI grammar is defined in
+   terms of characters.  Each literal in the grammar corresponds to the
+   character it represents, rather than to the octet encoding of that
+   character in any particular coded character set.  How a URI is
+   represented in terms of bits and bytes on the wire is dependent upon
+   the character encoding of the protocol used to transport it, or the
+   charset of the document which contains it.
+
+   The following definitions are common to many elements:
+
!   This BNF also describes the generic-RL syntax for valid base URLs.
!   Note that this differs from the URL syntax defined in RFC 1738 [2] in
!   that all schemes are required to use a single set of reserved
!   characters and use them consistently within the major URL components.
 
!   URL         = ( absoluteURL | relativeURL ) [ "#" fragment ]
 
!   absoluteURL = generic-RL | ( scheme ":" *( uchar | reserved ) )

!   generic-RL  = scheme ":" relativeURL
!
!   relativeURL = net_path | abs_path | rel_path
!
!   net_path    = "//" net_loc [ abs_path ]
!   abs_path    = "/"  rel_path
!   rel_path    = [ path ] [ ";" params ] [ "?" query ]
!
!   path        = fsegment *( "/" segment )
!   fsegment    = 1*pchar
!   segment     =  *pchar
 
!   params      = param *( ";" param )
!   param       = *( pchar | "/" )
+
 
!   scheme      = 1*( alpha | digit | "+" | "-" | "." )
!   net_loc     =  *( pchar | ";" | "?" )
!   query       =  *( uchar | reserved )
!   fragment    =  *( uchar | reserved )
!   pchar       = uchar | ":" | "@" | "&" | "="
!   uchar       = unreserved | escape
!   unreserved  = alpha | digit | safe | extra
 
!   escape      = "%" hex hex
!   hex         = digit | "A" | "B" | "C" | "D" | "E" | "F" |
!                         "a" | "b" | "c" | "d" | "e" | "f"
 
!   alpha       = lowalpha | hialpha
+      alpha    = lowalpha | upalpha
+
!+      lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" |
!+                 "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
!+                 "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
+
!   hialpha     = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
+      upalpha  = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
!+                 "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
!+                 "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"
+
+
!+      digit    = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
!+                 "8" | "9"
+
+      alphanum = alpha | digit
!   safe        = "$" | "-" | "_" | "." | "+"
!   extra       = "!" | "*" | "'" | "(" | ")" | ","
!   national    = "{" | "}" | "|" | "\" | "^" | "~" | "[" | "]" | "`"
!   reserved    = ";" | "/" | "?" | ":" | "@" | "&" | "="
!   punctuation = "<" | ">" | "#" | "%" | <">
+
+   The complete URI syntax is collected in Appendix A.
 
-2.2. URL Character Encoding Issues
-
-   URLs are sequences of characters, i.e., letters, digits, and special
-   characters. A URLs may be represented in a variety of ways: e.g., ink
-   on paper, or a sequence of octets in a coded character set. The
-   interpretation of a URL depends only on the identity of the
-   characters used.
-
-   In most URL schemes, the sequences of characters in different parts
-   of a URL are used to represent sequences of octets used in Internet
-   protocols. For example, in the ftp scheme, the host name, directory
-   name and file names are such sequences of octets, represented by
-   parts of the URL.  Within those parts, an octet may be represented by
-   the chararacter which has that octet as its code within the US-ASCII
-   [20] coded character set.
-
-   In addition, octets may be encoded by a character triplet consisting
-   of the character "%" followed by the two hexadecimal digits (from
-   "0123456789ABCDEF") which forming the hexadecimal value of the octet.
-   (The characters "abcdef" may also be used in hexadecimal encodings.)
-
-   Octets must be encoded if they have no corresponding graphic
-   character within the US-ASCII coded character set, if the use of the
-   corresponding character is unsafe, or if the corresponding character
-   is reserved for some other interpretation within the particular URL
-   scheme.
-@@(ry
+2. URI Characters and Escape Sequences
+
+   URI consist of a restricted set of characters, primarily chosen to
+   aid transcribability and usability both in computer systems and in
+   non-computer communications. Characters used conventionally as
+   delimiters around URI were excluded.  The restricted set of
+   characters consists of digits, letters, and a few graphic symbols
+   were chosen from those common to most of the character encodings and
+   input facilities available to Internet users.
+
+      uric          = reserved | unreserved | escaped
+
+   Within a URI, characters are either used as delimiters, or to
+   represent strings of data (octets) within the delimited portions.
+   Octets are either represented directly by a character (using the US-
+   ASCII character for that octet [ASCII]) or by an escape encoding.
+   This representation is elaborated below.
+
+2.1 URI and non-ASCII characters
+
+   The relationship between URI and characters has been a source of
+   confusion for characters that are not part of US-ASCII. To describe
+   the relationship, it is useful to distinguish between a "character"
+   (as a distinguishable semantic entity) and an "octet" (an 8-bit
+   byte). There are two mappings, one from URI characters to octets, and
+   a second from octets to original characters:
+
+   URI character sequence->octet sequence->original character sequence
+
+   A URI is represented as a sequence of characters, not as a sequence
+   of octets. That is because URI might be "transported" by means that
+   are not through a computer network, e.g., printed on paper, read over
+   the radio, etc.
+
+   A URI scheme may define a mapping from URI characters to octets;
+   whether this is done depends on the scheme. Commonly, within a
+   delimited component of a URI, a sequence of characters may be used to
+   represent a sequence of octets. For example, the character "a"
+   represents the octet 97 (decimal), while the character sequence "%",
+   "0", "a" represents the octet 10 (decimal).
+
+   There is a second translation for some resources: the sequence of
+   octets defined by a component of the URI is subsequently used to
+   represent a sequence of characters. A 'charset' defines this mapping.
+   There are many charsets in use in Internet protocols. For example,
+   UTF-8 [UTF-8] defines a mapping from sequences of octets to sequences
+   of characters in the repertoire of ISO 10646.
+
+   In the simplest case, the original character sequence contains only
+   characters that are defined in US-ASCII, and the two levels of
+   mapping are simple and easily invertible: each 'original character'
+   is represented as the octet for the US-ASCII code for it, which is,
+   in turn, represented as either the US-ASCII character, or else the
+   "%" escape sequence for that octet.
+
+   For original character sequences that contain non-ASCII characters,
+   however, the situation is more difficult. Internet protocols that
+   transmit octet sequences intended to represent character sequences
+   are expected to provide some way of identifying the charset used, if
+   there might be more than one [RFC2277].  However, there is currently
+   no provision within the generic URI syntax to accomplish this
+   identification. An individual URI scheme may require a single
+   charset, define a default charset, or provide a way to indicate the
+   charset used.
+
+   It is expected that a systematic treatment of character encoding
+   within URI will be developed as a future modification of this
+   specification.
+
@@ RFC 1738 2.2
-   Reserved:
-
-   Many URL schemes reserve certain characters for a special meaning:
-   their appearance in the scheme-specific part of the URL has a
-   designated semantics. If the character corresponding to an octet is
-   reserved in a scheme, the octet must be encoded.  The characters ";",
-   "/", "?", ":", "@", "=" and "&" are the characters which may be
-   reserved for special meaning within a scheme. No other characters may
-   be reserved within a scheme.

-   Usually a URL has the same interpretation when an octet is
-   represented by a character and when it encoded. However, this is not
-   true for reserved characters: encoding a character reserved for a
-   particular scheme may change the semantics of a URL.
-
-   Thus, only alphanumerics, the special characters "$-_.+!*'(),", and
-   reserved characters used for their reserved purposes may be used
-   unencoded within a URL.
-
-   On the other hand, characters that are not required to be encoded
-   (including alphanumerics) may be encoded within the scheme-specific
-   part of a URL, as long as they are not being used for a reserved
-   purpose.

+2.2. Reserved Characters

+   Many URI include components consisting of or delimited by, certain
+   special characters.  These characters are called "reserved", since
+   their usage within the URI component is limited to their reserved
+   purpose.  If the data for a URI component would conflict with the
+   reserved purpose, then the conflicting data must be escaped before
+   forming the URI.
+
+      reserved    = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
+                    "$" | ","

+   The "reserved" syntax class above refers to those characters that are
+   allowed within a URI, but which may not be allowed within a
+   particular component of the generic URI syntax; they are used as
+   delimiters of the components described in Section 3.
+
+   Characters in the "reserved" set are not reserved in all contexts.
+   The set of characters actually reserved within any given URI
+   component is defined by that component. In general, a character is
+   reserved if the semantics of the URI changes if the character is
+   replaced with its escaped US-ASCII encoding.
+
+2.3. Unreserved Characters
+
+   Data characters that are allowed in a URI but do not have a reserved
+   purpose are called unreserved.  These include upper and lower case
+   letters, decimal digits, and a limited set of punctuation marks and
+   symbols.
+
+      unreserved  = alphanum | mark
+
+      mark        = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
+
+   Unreserved characters can be escaped without changing the semantics
+   of the URI, but this should not be done unless the URI is being used
+   in a context that does not allow the unescaped character to appear.
+
+2.4. Escape Sequences
+
+   Data must be escaped if it does not have a representation using an
+   unreserved character; this includes data that does not correspond to
+   a printable character of the US-ASCII coded character set, or that
+   corresponds to any US-ASCII character that is disallowed, as
+   explained below.
+
+2.4.1. Escaped Encoding
+
+   An escaped octet is encoded as a character triplet, consisting of the
+   percent character "%" followed by the two hexadecimal digits
+   representing the octet code. For example, "%20" is the escaped
+   encoding for the US-ASCII space character.
+
+      escaped     = "%" hex hex
+      hex         = digit | "A" | "B" | "C" | "D" | "E" | "F" |
+                            "a" | "b" | "c" | "d" | "e" | "f"
+
+2.4.2. When to Escape and Unescape
+
+   A URI is always in an "escaped" form, since escaping or unescaping a
+   completed URI might change its semantics.  Normally, the only time
+   escape encodings can safely be made is when the URI is being created
+   from its component parts; each component may have its own set of
+   characters that are reserved, so only the mechanism responsible for
+   generating or interpreting that component can determine whether or
+   not escaping a character will change its semantics. Likewise, a URI
+   must be separated into its components before the escaped characters
+   within those components can be safely decoded.
+
+   In some cases, data that could be represented by an unreserved
+   character may appear escaped; for example, some of the unreserved
+   "mark" characters are automatically escaped by some systems.  If the
+   given URI scheme defines a canonicalization algorithm, then
+   unreserved characters may be unescaped according to that algorithm.
+   For example, "%7e" is sometimes used instead of "~" in an http URL
+   path, but the two are equivalent for an http URL.
+
+   Because the percent "%" character always has the reserved purpose of
+   being the escape indicator, it must be escaped as "%25" in order to
+   be used as data within a URI.  Implementers should be careful not to
+   escape or unescape the same string more than once, since unescaping
+   an already unescaped string might lead to misinterpreting a percent
+   data character as another escaped character, or vice versa in the
+   case of escaping an already escaped string.
+
-@@2.2
-   No corresponding graphic US-ASCII:
-
-   URLs are written only with the graphic printable characters of the
-   US-ASCII coded character set. The octets 80-FF hexadecimal are not
-   used in US-ASCII, and the octets 00-1F and 7F hexadecimal represent
-   control characters; these must be encoded.
+2.4.3. Excluded US-ASCII Characters
+
+   Although they are disallowed within the URI syntax, we include here a
+   description of those US-ASCII characters that have been excluded and
+   the reasons for their exclusion.
+
+   The control characters in the US-ASCII coded character set are not
+   used within a URI, both because they are non-printable and because
+   they are likely to be misinterpreted by some control mechanisms.
+
+   control     = <US-ASCII coded characters 00-1F and 7F hexadecimal>
+
-@@2.2
-   Unsafe:
-
-   Characters can be unsafe for a number of reasons.  The space
-   character is unsafe because significant spaces may disappear and
-   insignificant spaces may be introduced when URLs are transcribed or
-   typeset or subjected to the treatment of word-processing programs.
-   The characters "<" and ">" are unsafe because they are used as the
-   delimiters around URLs in free text; the quote mark (""") is used to
-   delimit URLs in some systems.  The character "#" is unsafe and should
-   always be encoded because it is used in World Wide Web and in other
-   systems to delimit a URL from a fragment/anchor identifier that might
-   follow it.  The character "%" is unsafe because it is used for
-   encodings of other characters.  Other characters are unsafe because
-   gateways and other transport agents are known to sometimes modify
-   such characters. These characters are "{", "}", "|", "\", "^", "~",
-   "[", "]", and "`".
-
-   All unsafe characters must always be encoded within a URL. For
-   example, the character "#" must be encoded within URLs even in
-   systems that do not normally deal with fragment or anchor
-   identifiers, so that if the URL is copied into another system that
-   does use them, it will not be necessary to change the URL encoding.

+   The space character is excluded because significant spaces may
+   disappear and insignificant spaces may be introduced when URI are
+   transcribed or typeset or subjected to the treatment of word-
+   processing programs.  Whitespace is also used to delimit URI in many
+   contexts.
+
+   space       = <US-ASCII coded character 20 hexadecimal>

+   The angle-bracket "<" and ">" and double-quote (") characters are
+   excluded because they are often used as the delimiters around URI in
+   text documents and protocol fields.  The character "#" is excluded
+   because it is used to delimit a URI from a fragment identifier in URI
+   references (Section 4). The percent character "%" is excluded because
+   it is used for the encoding of escaped characters.
+
+   delims      = "<" | ">" | "#" | "%" | <">
+
+   Other characters are excluded because gateways and other transport
+   agents are known to sometimes modify such characters, or they are
+   used as delimiters.
+
+   unwise      = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"
+
+   Data corresponding to excluded characters must be escaped in order to
+   be properly represented within a URI.
+
!2.  Relative URL Syntax
!
!   The syntax for relative URLs is a shortened form of that for absolute
!   URLs [2], where some prefix of the URL is missing and certain path
!   components ("." and "..") have a special meaning when interpreting a
!   relative path.  Because a relative URL may appear in any context that
!   could hold an absolute URL, systems that support relative URLs must
!   be able to recognize them as part of the URL parsing process.
!
!   Although this document does not seek to define the overall URL
!   syntax, some discussion of it is necessary in order to describe the
!   parsing of relative URLs.  In particular, base documents can only
!   make use of relative URLs when their base URL fits within the
!   generic-RL syntax described below.  Although some URL schemes do not
!   require this generic-RL syntax, it is assumed that any document which
!   contains a relative reference does have a base URL that obeys the
!   syntax.  In other words, relative URLs cannot be used within
!   documents that have unsuitable base URLs.
!
!2.1.  URL Syntactic Components
!
!   The URL syntax is dependent upon the scheme.  Some schemes use
!   reserved characters like "?" and ";" to indicate special components,
!   while others just consider them to be part of the path.  However,
!   there is enough uniformity in the use of URLs to allow a parser to
!   resolve relative URLs based upon a single, generic-RL syntax.  This
!   generic-RL syntax consists of six components:
!
!      <scheme>://<net_loc>/<path>;<params>?<query>#<fragment>
!
!   each of which, except <scheme>, may be absent from a particular URL.
!   These components are defined as follows (a complete BNF is provided
!   in Section 2.2):
!
!      scheme ":"   ::= scheme name, as per Section 2.1 of RFC 1738 [2].
!
!      "//" net_loc ::= network location and login information, as per
!                       Section 3.1 of RFC 1738 [2].
!
!      "/" path     ::= URL path, as per Section 3.1 of RFC 1738 [2].
!
!      ";" params   ::= object parameters (e.g., ";type=a" as in
!                       Section 3.2.2 of RFC 1738 [2]).
!
!      "?" query    ::= query information, as per Section 3.3 of
!                       RFC 1738 [2].
!
!      "#" fragment ::= fragment identifier.
!
!   Note that the fragment identifier (and the "#" that precedes it) is
!   not considered part of the URL.  However, since it is commonly used
!   within the same string context as a URL, a parser must be able to
!   recognize the fragment when it is present and set it aside as part of
!   the parsing process.
!
!   The order of the components is important.  If both <params> and
!   <query> are present, the <query> information must occur after the
!   <params>.
!

-2.1. The main parts of URLs
+3. URI Syntactic Components
-
-   A full BNF description of the URL syntax is given in Section 5.
-
+
+   The URI syntax is dependent upon the scheme. 
In general, 
-   URLs
+   absolute URI
are written as follows:
+
<scheme>:<scheme-specific-part>
+
-   A URL
+   An absolute URI
contains the name of the scheme being used (<scheme>) followed by a colon
+   (":")
and then a string (the <scheme-specific-part>) whose
interpretation depends on the scheme.

-@@ (ry
+
+   The URI syntax does not require that the scheme-specific-part have
+   any general structure or set of semantics which is common among all
+   URI.  However, a subset of URI do share a common syntax for
+   representing hierarchical relationships within the namespace.  This
+   "generic URI" syntax consists of a sequence of four main components:
+
+      <scheme>://<authority><path>?<query>
+
+   each of which, except <scheme>, may be absent from a particular URI.
+   For example, some URI schemes do not allow an <authority> component,
+   and others do not use a <query> component.
+
+      absoluteURI   = scheme ":" ( hier_part | opaque_part )
+
-3.2.4 Hierarchy
+   URI that are hierarchical in nature use the slash "/" character for
+   separating hierarchical components.
For some file systems, 
-   the "/" used to denote the hierarchical structure of the URL corresponds to the
+   a "/"  character (used to denote the hierarchical structure of a URI) is the
delimiter used to construct a file name hierarchy, and thus
-  , the filename will look similar to the URL path.
+   the URI path will look similar to a file pathname.
This does NOT 
-   mean that the URL is a Unix filename.
+   imply that the resource is a file or that the URI maps to an actual filesystem pathname.
+
+      hier_part     = ( net_path | abs_path ) [ "?" query ]
+
+      net_path      = "//" authority [ abs_path ]
+
+      abs_path      = "/"  path_segments
+
+   URI that do not make use of the slash "/" character for separating
+   hierarchical components are considered opaque by the generic URI
+   parser.
+
+      opaque_part   = uric_no_slash *uric
+
+      uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
+                      "&" | "=" | "+" | "$" | ","
+
+   We use the term <path> to refer to both the <abs_path> and
+   <opaque_part> constructs, since they are mutually exclusive for any
+   given URI and can be parsed as a single component.
+
-2.3 Hierarchical schemes and relative links
-
-   In some cases, URLs are used to locate resources that contain
-   pointers to other resources. In some cases, those pointers are
-   represented as relative links where the expression of the location of
-   the second resource is in terms of "in the same place as this one
-   except with the following relative path". Relative links are not
-   described in this document. However, the use of relative links
-   depends on the original URL containing a hierarchical structure
-   against which the relative link is based.
-
-   Some URL schemes (such as the ftp, http, and file schemes) contain
-   names that can be considered hierarchical; the components of the
-   hierarchy are separated by "/".
-
!2.4.2.  Parsing the Scheme
!
!   If the parse string contains a colon ":" after the first character
!   and before any characters not allowed as part of a scheme name (i.e.,
!   any not an alphanumeric, plus "+", period ".", or hyphen "-"), the
!   <scheme> of the URL is the substring of characters up to but not
!   including the first colon.  These characters and the colon are then
!   removed from the parse string before continuing.
+3.1. Scheme Component
+

+   Just as there are many different methods of access to resources,
+   there are a variety of schemes for identifying such resources.  The
+   URI syntax consists of a sequence of components separated by reserved
+   characters, with the first component defining the semantics for the
+   remainder of the URI string.
+
-@@2.1
Scheme names consist of a sequence of characters
-   . The
+   beginning with a lower case letter and followed by any combination of
lower case letters
-   "a"--"z"
, digits,
- and the characters
plus ("+"), period ("."),
-   and hyphen ("-")
+   or
hyphen ("-")
- are allowed
. For resiliency, programs interpreting
-   URLs
+   URI
should treat upper case letters as equivalent to
lower case in scheme names (e.g., allow "HTTP" as well as "http").

+      scheme        = alpha *( alpha | digit | "+" | "-" | "." )
+
+   Relative URI references are distinguished from absolute URI in that
+   they do not begin with a scheme name.  Instead, the scheme is
+   inherited from the base URI, as described in Section 5.2.
+
!2.4.3.  Parsing the Network Location/Login
!
!   If the parse string begins with a double-slash "//", then the
!   substring of characters after the double-slash and up to, but not
!   including, the next slash "/" character is the network location/login
!   (<net_loc>) of the URL.  If no trailing slash "/" is present, the
!   entire remaining parse string is assigned to <net_loc>.  The double-
!   slash and <net_loc> are removed from the parse string before
!   continuing.
+3.2. Authority Component
+
+   Many URI schemes include a top hierarchical element for a naming
+   authority, such that the namespace defined by the remainder of the
+   URI is governed by that authority.  This authority component is
+   typically defined by an Internet-based server or a scheme-specific
+   registry of naming authorities.
+
+      authority     = server | reg_name
+
+   The authority component is preceded by a double slash "//" and is
+   terminated by the next slash "/", question-mark "?", or by the end of
+   the URI.  Within the authority component, the characters ";", ":",
+   "@", "?", and "/" are reserved.
+
+   An authority component is not required for a URI scheme to make use
+   of relative references.  A base URI without an authority component
+   implies that any relative reference will also be without an authority
+   component.
+
+3.2.1. Registry-based Naming Authority
+
+   The structure of a registry-based naming authority is specific to the
+   URI scheme, but constrained to the allowed characters for an
+   authority component.
+
+      reg_name      = 1*( unreserved | escaped | "$" | "," |
+                          ";" | ":" | "@" | "&" | "=" | "+" )
+
-3.1. Common Internet Scheme Syntax
-
-   While the syntax for the rest of the URL may vary depending on the
-   particular scheme selected, URL schemes that involve the direct use
-   of an IP-based protocol to a specified host on the Internet use a
-   common syntax for the scheme-specific data:
-
-        //<user>:<password>@<host>:<port>/<url-path>
-
-   Some or all of the parts "<user>:<password>@", ":<password>",
-   ":<port>", and "/<url-path>" may be excluded.  The scheme specific
-   data start with a double slash "//" to indicate that it complies with
-   the common Internet scheme syntax. The different components obey the
-   following rules:
-
-    user
-        An optional user name. Some schemes (e.g., ftp) allow the
-        specification of a user name.
-
-    password
-        An optional password. If present, it follows the user
-        name separated from it by a colon.
-
-   The user name (and password), if present, are followed by a
-   commercial at-sign "@". Within the user and password field, any ":",
-   "@", or "/" must be encoded.
-
-   Note that an empty user name or password is different than no user
-   name or password; there is no way to specify a password without
-   specifying a user name. E.g., <URL:ftp://@host.com/> has an empty
-   user name and no password, <URL:ftp://host.com/> has no user name,
-   while <URL:ftp://foo:@host.com/> has a user name of "foo" and an
-   empty password.
-
-    host
-        The fully qualified domain name of a network host, or its IP
-        address as a set of four decimal digit groups separated by
-        ".". Fully qualified domain names take the form as described
-        in Section 3.5 of RFC 1034 [13] and Section 2.1 of RFC 1123
-        [5]: a sequence of domain labels separated by ".", each domain
-        label starting and ending with an alphanumerical character and
-        possibly also containing "-" characters. The rightmost domain
-        label will never start with a digit, though, which
-        syntactically distinguishes all domain names from the IP
-        addresses.
-
-    port
-        The port number to connect to. Most schemes designate
-        protocols that have a default port number. Another port number
-        may optionally be supplied, in decimal, separated from the
-        host by a colon. If the port is omitted, the colon is as well.
-
-    url-path
-        The rest of the locator consists of data specific to the
-        scheme, and is known as the "url-path". It supplies the
-        details of how the specified resource can be accessed. Note
-        that the "/" between the host (or port) and the url-path is
-        NOT part of the url-path.
-
-   The url-path syntax depends on the scheme being used, as does the
-   manner in which it is interpreted.
-
+3.2.2. Server-based Naming Authority
+
+   URL schemes that involve the direct use of an IP-based protocol to a
+   specified server on the Internet use a common syntax for the server
+   component of the URI's scheme-specific data:
+
+      <userinfo>@<host>:<port>
+
+   where <userinfo> may consist of a user name and, optionally, scheme-
+   specific information about how to gain authorization to access the
+   server.  The parts "<userinfo>@" and ":<port>" may be omitted.
+
+      server        = [ [ userinfo "@" ] hostport ]
+
+   The user information, if present, is followed by a commercial at-sign
+   "@".
+
+      userinfo      = *( unreserved | escaped |
+                         ";" | ":" | "&" | "=" | "+" | "$" | "," )
+
+   Some URL schemes use the format "user:password" in the userinfo
+   field. This practice is NOT RECOMMENDED, because the passing of
+   authentication information in clear text (such as URI) has proven to
+   be a security risk in almost every case where it has been used.
+
+   The host is a domain name of a network host, or its IPv4 address as a
+   set of four decimal digit groups separated by ".".  Literal IPv6
+   addresses are not supported.
+
+      hostport      = host [ ":" port ]
+      host          = hostname | IPv4address
+      hostname      = *( domainlabel "." ) toplabel [ "." ]
+      domainlabel   = alphanum | alphanum *( alphanum | "-" ) alphanum
+      toplabel      = alpha | alpha *( alphanum | "-" ) alphanum
+      IPv4address   = 1*digit "." 1*digit "." 1*digit "." 1*digit
+      port          = *digit
+
+   Hostnames take the form described in Section 3 of [RFC1034] and
+   Section 2.1 of [RFC1123]: a sequence of domain labels separated by
+   ".", each domain label starting and ending with an alphanumeric
+   character and possibly also containing "-" characters.  The rightmost
+   domain label of a fully qualified domain name will never start with a
+   digit, thus syntactically distinguishing domain names from IPv4
+   addresses, and may be followed by a single "." if it is necessary to
+   distinguish between the complete domain name and any local domain.
+   To actually be "Uniform" as a resource locator, a URL hostname should
+   be a fully qualified domain name.  In practice, however, the host
+   component may be a local domain literal.
+
+      Note: A suitable representation for including a literal IPv6
+      address as the host part of a URL is desired, but has not yet been
+      determined or implemented in practice.
+
+   The port is the network port number for the server.  Most schemes
+   designate protocols that have a default port number.  Another port
+   number may optionally be supplied, in decimal, separated from the
+   host by a colon.  If the port is omitted, the default port number is
+   assumed.
+
!2.4.5.  Parsing the Parameters
!
!   If the parse string contains a semicolon ";" character, then the
!   substring after the first (left-most) semicolon ";" and up to the end
!   of the parse string is the parameters (<params>).  If the semicolon
!   is the last character, or no semicolon is present, then <params> is
!   empty.  The matched substring, including the semicolon character, is
!   removed from the parse string before continuing.
!
!2.4.6.  Parsing the Path
!
!   After the above steps, all that is left of the parse string is the
!   URL <path> and the slash "/" that may precede it.  Even though the
!   initial slash is not part of the URL path, the parser must remember
!   whether or not it was present so that later processes can
!   differentiate between relative and absolute paths.  Often this is
!   done by simply storing the preceding slash along with the path.
+3.3. Path Component
+
+   The path component contains data, specific to the authority (or the
+   scheme if there is no authority component), identifying the resource
+   within the scope of that scheme and authority.
+
+      path          = [ abs_path | opaque_part ]
+
+      path_segments = segment *( "/" segment )
+      segment       = *pchar *( ";" param )
+      param         = *pchar
+
+      pchar         = unreserved | escaped |
+                      ":" | "@" | "&" | "=" | "+" | "$" | ","
+
+   The path may consist of a sequence of path segments separated by a
+   single slash "/" character.  Within a path segment, the characters
+   "/", ";", "=", and "?" are reserved.  Each path segment may include a
+   sequence of parameters, indicated by the semicolon ";" character.
+   The parameters are not significant to the parsing of relative
+   references.
!2.4.4.  Parsing the Query Information
!
!   If the parse string contains a question mark "?" character, then the
!   substring after the first (left-most) question mark "?" and up to the
!   end of the parse string is the <query> information.  If the question
!   mark is the last character, or no question mark is present, then the
!   query information is empty.  The matched substring, including the
!   question mark character, is removed from the parse string before
!   continuing.
+
+3.4. Query Component
+
+   The query component is a string of information to be interpreted by
+   the resource.
+
+      query         = *uric
+
+   Within a query component, the characters ";", "/", "?", ":", "@",
+   "&", "=", "+", ",", and "$" are reserved.
+
+4. URI References
+
+   The term "URI-reference" is used here to denote the common usage of a
+   resource identifier.  A URI reference may be absolute or relative,
+   and may have additional information attached in the form of a
+   fragment identifier.  However, "the URI" that results from such a
+   reference includes only the absolute URI after the fragment
+   identifier (if any) is removed and after any relative URI is resolved
+   to its absolute form.  Although it is possible to limit the
+   discussion of URI syntax and semantics to that of the absolute
+   result, most usage of URI is within general URI references, and it is
+   impossible to obtain the URI from such a reference without also
+   parsing the fragment and resolving the relative form.
+
+      URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
+
+   The syntax for relative URI is a shortened form of that for absolute
+   URI, where some prefix of the URI is missing and certain path
+   components ("." and "..") have a special meaning when, and only when,
+   interpreting a relative path.  The relative URI syntax is defined in
+   Section 5.
+
!2.4.1.  Parsing the Fragment Identifier
!
!   If the parse string contains a crosshatch "#" character, then the
!   substring after the first (left-most) crosshatch "#" and up to the
!   end of the parse string is the <fragment> identifier.  If the
!   crosshatch is the last character, or no crosshatch is present, then
!   the fragment identifier is empty.  The matched substring, including
!   the crosshatch character, is removed from the parse string before
!   continuing.
!
!   Note that the fragment identifier is not considered part of the URL.
!   However, since it is often attached to the URL, parsers must be able
!   to recognize and set aside fragment identifiers as part of the
!   process.
+4.1. Fragment Identifier
+
+   When a URI reference is used to perform a retrieval action on the
+   identified resource, the optional fragment identifier, separated from
+   the URI by a crosshatch ("#") character, consists of additional
+   reference information to be interpreted by the user agent after the
+   retrieval action has been successfully completed.  As such, it is not
+   part of a URI, but is often used in conjunction with a URI.
+
+      fragment      = *uric
+
+   The semantics of a fragment identifier is a property of the data
+   resulting from a retrieval action, regardless of the type of URI used
+   in the reference.  Therefore, the format and interpretation of
+   fragment identifiers is dependent on the media type [RFC2046] of the
+   retrieval result.  The character restrictions described in Section 2
+   for URI also apply to the fragment in a URI-reference.  Individual
+   media types may define additional restrictions or structure within
+   the fragment for specifying different types of "partial views" that
+   can be identified within that media type.
+
+   A fragment identifier is only meaningful when a URI reference is
+   intended for retrieval and the result of that retrieval is a document
+   for which the identified fragment is consistently defined.
+
+4.2. Same-document References
+
+   A URI reference that does not contain a URI is a reference to the
+   current document.  In other words, an empty URI reference within a
+   document is interpreted as a reference to the start of that document,
+   and a reference containing only a fragment identifier is a reference
+   to the identified fragment of that document.  Traversal of such a
+   reference should not result in an additional retrieval action.
+   However, if the URI reference occurs in a context that is always
+   intended to result in a new request, as in the case of HTML's FORM
+   element, then an empty URI reference represents the base URI of the
+   current document and should be replaced by that URI when transformed
+   into a request.
+
!2.4.  Parsing a URL
+4.3. Parsing a URI Reference
!
!   An accepted method for parsing URLs is useful to clarify the
!   generic-RL syntax of Section 2.2 and to describe the algorithm for
!   resolving relative URLs presented in Section 4.  This section
!   describes the parsing rules for breaking down a URL (relative or
!   absolute) into the component parts described in Section 2.1.  The
!   rules assume that the URL has already been separated from any
!   surrounding text and copied to a "parse string".  The rules are
!   listed in the order in which they would be applied by the parser.
+
+   A URI reference is typically parsed according to the four main
+   components and fragment identifier in order to determine what
+   components are present and whether the reference is relative or
+   absolute.  The individual components are then parsed for their
+   subparts and, if not opaque, to verify their validity.
+
+   Although the BNF defines what is allowed in each component, it is
+   ambiguous in terms of differentiating between an authority component
+   and a path component that begins with two slash characters.  The
+   greedy algorithm is used for disambiguation: the left-most matching
+   rule soaks up as much of the URI reference string as it is capable of
+   matching.  In other words, the authority component wins.
+
+   Readers familiar with regular expressions should see Appendix B for a
+   concrete parsing example and test oracle.
+
+5. Relative URI References
+
+   It is often the case that a group or "tree" of documents has been
+   constructed to serve a common purpose; the vast majority of URI in
+   these documents point to resources within the tree rather than
+   outside of it.  Similarly, documents located at a particular site are
+   much more likely to refer to other resources at that site than to
+   resources at remote sites.
+
+   Relative addressing of URI allows document trees to be partially
+   independent of their location and access scheme.  For instance, it is
+   possible for a single set of hypertext documents to be simultaneously
+   accessible and traversable via each of the "file", "http", and "ftp"
+   schemes if the documents refer to each other using relative URI.
+   Furthermore, such document trees can be moved, as a whole, without
+   changing any of the relative references.  Experience within the WWW
+   has demonstrated that the ability to perform relative referencing is
+   necessary for the long-term usability of embedded URI.
+
+   The syntax for relative URI takes advantage of the <hier_part> syntax
+   of <absoluteURI> (Section 3) in order to express a reference that is
+   relative to the namespace of another hierarchical URI.
+
+      relativeURI   = ( net_path | abs_path | rel_path ) [ "?" query ]
+
+   A relative reference beginning with two slash characters is termed a
+   network-path reference, as defined by <net_path> in Section 3.  Such
+   references are rarely used.
+
+   A relative reference beginning with a single slash character is
+   termed an absolute-path reference, as defined by <abs_path> in
+   Section 3.
+
+   A relative reference that does not begin with a scheme name or a
+   slash character is termed a relative-path reference.
+
+      rel_path      = rel_segment [ abs_path ]
+
+      rel_segment   = 1*( unreserved | escaped |
+                          ";" | "@" | "&" | "=" | "+" | "$" | "," )
+
+   Within a relative-path reference, the complete path segments "." and
+   ".." have special meanings: "the current hierarchy level" and "the
+   level above this hierarchy level", respectively.  Although this is
+   very similar to their use within Unix-based filesystems to indicate
+   directory levels, these path components are only considered special
+   when resolving a relative-path reference to its absolute form
+   (Section 5.2).
+
+   Authors should be aware that a path segment which contains a colon
+   character cannot be used as the first segment of a relative URI path
+   (e.g., "this:that"), because it would be mistaken for a scheme name.
+
+   It is therefore necessary to precede such segments with other
+   segments (e.g., "./this:that") in order for them to be referenced as
+   a relative path.
+
+   It is not necessary for all URI within a given scheme to be
+   restricted to the <hier_part> syntax, since the hierarchical
+   properties of that syntax are only necessary when relative URI are
+   used within a particular document.  Documents can only make use of
+   relative URI when their base URI fits within the <hier_part> syntax.
+   It is assumed that any document which contains a relative reference
+   will also have a base URI that obeys the syntax.  In other words,
+   relative URI cannot be used within a document that has an unsuitable
+   base URI.
+
+   Some URI schemes do not allow a hierarchical syntax matching the
+   <hier_part> syntax, and thus cannot use relative references.
+
!3.  Establishing a Base URL
+5.1. Establishing a Base URI
+
!
!   The term "relative URL" implies that there exists some absolute "base URL"
+   The term "relative URI" implies that there exists some absolute "base URI"
against which the relative reference is applied.  Indeed, the
!   base URL is necessary to define the semantics of any embedded relative URLs
+   base URI is necessary to define the semantics of any relative URI reference
; without it, a relative reference is meaningless.  In order for relative
!   URLs to be usable within a document, the base URL
+   URI to be usable within a document, the base URI
of that document must be known to the parser.
 
!   The base URL
+   The base URI
of a document can be established in one of four ways,
    listed below in order of precedence.  The order of precedence can be
!   thought of in terms of layers, where the innermost defined base URL
+   thought of in terms of layers, where the innermost defined base URI
    has the highest precedence.  This can be visualized graphically as:
 
       .----------------------------------------------------------.
       |  .----------------------------------------------------.  |
       |  |  .----------------------------------------------.  |  |
       |  |  |  .----------------------------------------.  |  |  |
+      |  |  |  |  .----------------------------------.  |  |  |  |
+      |  |  |  |  |       <relative_reference>       |  |  |  |  |
+      |  |  |  |  `----------------------------------'  |  |  |  |
!      |  |  |  |   (3.1) Base URL embedded in the       |  |  |  |
+      |  |  |  | (5.1.1) Base URI embedded in the       |  |  |  |
       |  |  |  |         document's content             |  |  |  |
       |  |  |  `----------------------------------------'  |  |  |
!      |  |  |   (3.2) Base URL of the encapsulating entity |  |  |
+      |  |  | (5.1.2) Base URI of the encapsulating entity |  |  |
       |  |  |         (message, document, or none).        |  |  |
       |  |  `----------------------------------------------'  |  |
!      |  |   (3.3) URL used to retrieve the entity            |  |
+      |  | (5.1.3) URI used to retrieve the entity            |  |
       |  `----------------------------------------------------'  |
!      |   (3.4) Base URL = "" (undefined)                        |
+      | (5.1.4) Default Base URI is application-dependent        |
       `----------------------------------------------------------'
 
!3.1.  Base URL within Document Content
+5.1.1. Base URI within Document Content
 
!   Within certain document media types, the base URL of the document can
+   Within certain document media types, the base URI of the document can
+   be embedded within the content itself such that it can be readily
+   obtained by a parser.  This can be useful for descriptive documents,
+   such as tables of content, which may be transmitted to others through
+   protocols other than their usual retrieval context (e.g., E-Mail or
+   USENET news).
+
    It is beyond the scope of this document to specify how, for each
!   media type, the base URL can be embedded.  It is assumed that user
+   media type, the base URI can be embedded.  It is assumed that user
    agents manipulating such media types will be able to obtain the
    appropriate syntax from that media type's specification.  An example
!   of how the base URL can be embedded in the Hypertext Markup Language
!   (HTML) [3] is provided in an Appendix (Section 10).
+   of how the base URI can be embedded in the Hypertext Markup Language
+   (HTML) [RFC1866] is provided in Appendix D.
+
!   Messages are considered to be composite documents.  The base URL of a
!   message can be specified within the message headers (or equivalent
!   tagged metainformation) of the message.  For protocols that make use
!   of message headers like those described in RFC 822 [5], we recommend
!   that the format of this header be:
!
!      base-header  = "Base" ":" "<URL:" absoluteURL ">"
!
!   where "Base" is case-insensitive and any whitespace (including that
!   used for line folding) inside the angle brackets is ignored.  For
!   example, the header field
!
!      Base: <URL:http://www.ics.uci.edu/Test/a/b/c>
!
!   would indicate that the base URL for that message is the string
!   "http://www.ics.uci.edu/Test/a/b/c".  The base URL for a message
!   serves as both the base for any relative URLs within the message
!   headers and the default base URL for documents enclosed within the
!   message, as described in the next section.
!
+   A mechanism for embedding the base URI within MIME container types
+   (e.g., the message and multipart types) is defined by MHTML
+   [RFC2110].
!   Protocols which do not use the RFC 822
+Protocols that do not use the MIME
message header syntax,
but which do allow some form of tagged metainformation to be included
    within messages, may define their own syntax for defining the base
!   URL as part of a message.
+   URI as part of a message.
 
!3.2.  Base URL from the Encapsulating Entity
+5.1.2. Base URI from the Encapsulating Entity
 
!   If no base URL is embedded, the base URL of a document is defined by
+   If no base URI is embedded, the base URI of a document is defined by
    the document's retrieval context.  For a document that is enclosed
    within another entity (such as a message or another document), the
!   retrieval context is that entity; thus, the default base URL of the
+   retrieval context is that entity; thus, the default base URI of the
!   document is the base URL of the entity in which the document is
+   document is the base URI of the entity in which the document is
    encapsulated.
 
!   Composite media types, such as the "multipart/*" and "message/*"
!   media types defined by MIME (RFC 1521, [4]), define a hierarchy of
!   retrieval context for their enclosed documents.  In other words, the
!   retrieval context of a component part is the base URL of the
!   composite entity of which it is a part.  Thus, a composite entity can
!   redefine the retrieval context of its component parts via the
!   inclusion of a base-header, and this redefinition applies recursively
!   for a hierarchy of composite parts.  Note that this might not change
!   the base URL of the components, since each component may include an
!   embedded base URL or base-header that takes precedence over the
!   retrieval context.
!
!3.3.  Base URL from the Retrieval URL
+5.1.3. Base URI from the Retrieval URI
 
!   If no base URL is embedded and the document is not encapsulated
+   If no base URI is embedded and the document is not encapsulated
    within some other entity (e.g., the top level of a composite entity),
!   then, if a URL was used to retrieve the base document, that URL shall
+   then, if a URI was used to retrieve the base document, that URI shall
!   be considered the base URL.  Note that if the retrieval was the
+   be considered the base URI.  Note that if the retrieval was the
!   result of a redirected request, the last URL used (i.e., that which
+   result of a redirected request, the last URI used (i.e., that which
!   resulted in the actual retrieval of the document) is the base URL.
+   resulted in the actual retrieval of the document) is the base URI.
!
!3.4.  Default Base URL
+5.1.4. Default Base URI
!
!   If none of the conditions described in Sections 3.1 -- 3.3 apply,
+   If none of the conditions described in Sections 5.1.1--5.1.3 apply,
!   then the base URL is considered to be the empty string and all
+   then the base URI is defined by the context of the application.
!   embedded URLs within that document are assumed to be absolute URLs.
+   Since this definition is necessarily application-dependent, failing
+   to define the base URI using one of the other methods may result in
+   the same content being interpreted differently by different types of
+   application.
 
    It is the responsibility of the distributor(s) of a document
!   containing relative URLs to ensure that the base URL for that
+   containing relative URI to ensure that the base URI for that
document can be established.  It must be emphasized that relative
!   URLs cannot be used reliably in situations where the document's base URL
+   URI cannot be used reliably in situations where the document's base URI
is not well-defined.
!
!4.  Resolving Relative URLs
+5.2. Resolving Relative References to Absolute Form
+
!
!   This section describes an example algorithm for resolving URLs
+   This section describes an example algorithm for resolving URI
!   within a context in which the URLs may be relative, such that the result is
+   references that might be relative to a given base URI.
!   always a URL in absolute form.  Although this algorithm cannot
!   guarantee that the resulting URL will equal that intended by the
!   original author, it does guarantee that any valid URL (relative or
!   absolute) can be consistently transformed to an absolute form given a
!   valid base URL.
!
+
+   The base URI is established according to the rules of Section 5.1 and
+   parsed into the four main components as described in Section 3.  Note
+   that only the scheme component is required to be present in the base
+   URI; the other components may be empty or undefined.  A component is
+   undefined if its preceding separator does not appear in the URI
+   reference; the path component is never undefined, though it may be
+   empty.  The base URI's query component is not used by the resolution
+   algorithm and may be discarded.
+
!   The following steps are performed in order:
+   For each URI reference, the following steps are performed in order:
+
!   Step 1: The base URL is established according to the rules of
!           Section 3.  If the base URL is the empty string (unknown),
!           the embedded URL is interpreted as an absolute URL and
!           we are done.

!   Step 2: Both the base and embedded URLs are parsed into their
!           component parts as described in Section 2.4.
!
!           a) If the embedded URL is entirely empty, it inherits the
!              entire base URL (i.e., is set equal to the base URL)
!              and we are done.
!
!           b) If the embedded URL starts with a scheme name, it is
!              interpreted as an absolute URL and we are done.
!
!           c) Otherwise, the embedded URL inherits the scheme of
!              the base URL.
!
!   Step 3: If the embedded URL's <net_loc> is non-empty, we skip to
!           Step 7.  Otherwise, the embedded URL inherits the <net_loc>
!           (if any) of the base URL.
!
!   Step 4: If the embedded URL path is preceded by a slash "/", the
!           path is not relative and we skip to Step 7.
!
!   Step 5: If the embedded URL path is empty (and not preceded by a
!           slash), then the embedded URL inherits the base URL path,
!           and
!
!           a) if the embedded URL's <params> is non-empty, we skip to
!              step 7; otherwise, it inherits the <params> of the base
!              URL (if any) and
!
!           b) if the embedded URL's <query> is non-empty, we skip to
!              step 7; otherwise, it inherits the <query> of the base
!              URL (if any) and we skip to step 7.
!
!   Step 6: The last segment of the base URL's path (anything
!           following the rightmost slash "/", or the entire path if no
!           slash is present) is removed and the embedded URL's path is
!           appended in its place.  The following operations are
!           then applied, in order, to the new path:
!
!           a) All occurrences of "./", where "." is a complete path
!              segment, are removed.
!
!           b) If the path ends with "." as a complete path segment,
!              that "." is removed.
!
!           c) All occurrences of "<segment>/../", where <segment> is a
!              complete path segment not equal to "..", are removed.
!              Removal of these path segments is performed iteratively,
!              removing the leftmost matching pattern on each iteration,
!              until no matching pattern remains.
!
!           d) If the path ends with "<segment>/..", where <segment> is a
!              complete path segment not equal to "..", that
!              "<segment>/.." is removed.
!
!   Step 7: The resulting URL components, including any inherited from
!           the base URL, are recombined to give the absolute form of
!           the embedded URL.
!
!   Parameters, regardless of their purpose, do not form a part of the
!   URL path and thus do not affect the resolving of relative paths.  In
!   particular, the presence or absence of the ";type=d" parameter on an
!   ftp URL does not affect the interpretation of paths relative to that
!   URL.  Fragment identifiers are only inherited from the base URL when
!   the entire embedded URL is empty.

+   1) The URI reference is parsed into the potential four components and
+      fragment identifier, as described in Section 4.3.
+
+   2) If the path component is empty and the scheme, authority, and
+      query components are undefined, then it is a reference to the
+      current document and we are done.  Otherwise, the reference URI's
+      query and fragment components are defined as found (or not found)
+      within the URI reference and not inherited from the base URI.
+
+   3) If the scheme component is defined, indicating that the reference
+      starts with a scheme name, then the reference is interpreted as an
+      absolute URI and we are done.  Otherwise, the reference URI's
+      scheme is inherited from the base URI's scheme component.
+
+      Due to a loophole in prior specifications [RFC1630], some parsers
+      allow the scheme name to be present in a relative URI if it is the
+      same as the base URI scheme.  Unfortunately, this can conflict
+      with the correct parsing of non-hierarchical URI.  For backwards
+      compatibility, an implementation may work around such references
+      by removing the scheme if it matches that of the base URI and the
+      scheme is known to always use the <hier_part> syntax.  The parser
+      can then continue with the steps below for the remainder of the
+      reference components.  Validating parsers should mark such a
+      misformed relative reference as an error.
+
+   4) If the authority component is defined, then the reference is a
+      network-path and we skip to step 7.  Otherwise, the reference
+      URI's authority is inherited from the base URI's authority
+      component, which will also be undefined if the URI scheme does not
+      use an authority component.
+
+   5) If the path component begins with a slash character ("/"), then
+      the reference is an absolute-path and we skip to step 7.
+
+   6) If this step is reached, then we are resolving a relative-path
+      reference.  The relative path needs to be merged with the base
+      URI's path.  Although there are many ways to do this, we will
+      describe a simple method using a separate string buffer.
+
+      a) All but the last segment of the base URI's path component is
+         copied to the buffer.  In other words, any characters after the
+         last (right-most) slash character, if any, are excluded.
+
+      b) The reference's path component is appended to the buffer
+         string.
+
+      c) All occurrences of "./", where "." is a complete path segment,
+         are removed from the buffer string.
+
+      d) If the buffer string ends with "." as a complete path segment,
+         that "." is removed.
+
+      e) All occurrences of "<segment>/../", where <segment> is a
+         complete path segment not equal to "..", are removed from the
+         buffer string.  Removal of these path segments is performed
+         iteratively, removing the leftmost matching pattern on each
+         iteration, until no matching pattern remains.
+
+      f) If the buffer string ends with "<segment>/..", where <segment>
+         is a complete path segment not equal to "..", that
+         "<segment>/.." is removed.
+
+      g) If the resulting buffer string still begins with one or more
+         complete path segments of "..", then the reference is
+         considered to be in error.  Implementations may handle this
+         error by retaining these components in the resolved path (i.e.,
+         treating them as part of the final URI), by removing them from
+         the resolved path (i.e., discarding relative levels above the
+         root), or by avoiding traversal of the reference.
+
+      h) The remaining buffer string is the reference URI's new path
+         component.
+
+   7) The resulting URI components, including any inherited from the
+      base URI, are recombined to give the absolute form of the URI
+      reference.  Using pseudocode, this would be
+
+         result = ""
+
+         if scheme is defined then
+             append scheme to result
+             append ":" to result
+
+         if authority is defined then
+             append "//" to result
+             append authority to result
+
+         append path to result
+
+         if query is defined then
+             append "?" to result
+             append query to result
+
+         if fragment is defined then
+             append "#" to result
+             append fragment to result
+
+         return result
+
+      Note that we must be careful to preserve the distinction between a
+      component that is undefined, meaning that its separator was not
+      present in the reference, and a component that is empty, meaning
+      that the separator was present and was immediately followed by the
+      next component separator or the end of the reference.
+
    The above algorithm is intended to provide an example by which the
    output of implementations can be tested -- implementation of the
    algorithm itself is not required.  For example, some systems may find
!   it more efficient to implement Step 6 as a pair of segment stacks
+   it more efficient to implement step 6 as a pair of segment stacks
!   being merged, rather than as a series of string pattern matches.
+   being merged, rather than as a series of string pattern replacements.
+
+      Note: Some WWW client applications will fail to separate the
+      reference's query component from its path component before merging
+      the base and reference paths in step 6 above.  This may result in
+      a loss of information if the query component contains the strings
+      "/../" or "/./".
+
+   Resolution examples are provided in Appendix C.
+
+6. URI Normalization and Equivalence
+
+   In many cases, different URI strings may actually identify the
+   identical resource. For example, the host names used in URL are
+   actually case insensitive, and the URL <http://www.XEROX.com> is
+   equivalent to <http://www.xerox.com>. In general, the rules for
+   equivalence and definition of a normal form, if any, are scheme
+   dependent. When a scheme uses elements of the common syntax, it will
+   also use the common syntax equivalence rules, namely that the scheme
+   and hostname are case insensitive and a URL with an explicit ":port",
+   where the port is the default for the scheme, is equivalent to one
+   where the port is elided.
+
!6.  Security Considerations
!
!   There are no security considerations in the use or parsing of
!   relative URLs.  However, once a relative URL has been resolved to its
!   absolute form, the same security considerations apply as those
!   described in RFC 1738 [2].
-6. Security Considerations
+7. Security Considerations
-
-   The URL scheme
+   A URI
does not in itself pose a security threat. 
Users should beware that there is no general guarantee that a URL
+   ,
-   which at one time
+   which at one time
-   points to a given object continues to do so, and does not
-   even at some later time point to a different object due to the
-   movement of objects on servers.
+ located a given resource, will continue to do so.  Nor is there any
+   guarantee that a URL will not locate a different resource at some
+   later point in time, due to the lack of any constraint on how a given
+   authority apportions its namespace.  Such a guarantee can only be
+   obtained from the person(s) controlling that namespace and the
+   resource in question.  A specific URI scheme may include additional
+   semantics, such as name persistence, if those semantics are required
+   of all naming authorities for that scheme.
+
-
-   A URL-related security threat is that it
+   It
is sometimes possible to construct a URL such that an attempt to perform a
-   harmless idempotent
+  seemingly harmless, idempotent
-   operation such as the retrieval of the object
+   operation, such as the retrieval of an entity associated with the resource,
will in fact cause a possibly damaging remote operation to occur.  The unsafe URL
is typically constructed by specifying a port number other than that
reserved for the network protocol in question.  The client unwittingly contacts a
-   server which
+   site that
is in fact running a different protocol.  The content of the URL contains instructions
-   which when interpreted according to this other protocol cause an unexpected
+   that, when interpreted according to this other protocol, cause an unexpected
-   operation. An example has been the use of gopher URLs to cause a rude
+   operation.  An example has been the use of a gopher URL to cause an unintended or impersonating
message to be sent via a SMTP server.

Caution should be used when using any URL 
-   which
+   that
specifies a port number other than the default for the protocol, especially when it is
a number within the reserved space.
 
-   Care should be taken when URLs contain embedded encoded
+   Care should be taken when a URL contains escaped
delimiters for a given protocol (for example, CR and LF characters for telnet
protocols) that these are not unescaped before transmission.  This
-   would violate the protocol but could be used to simulate an
+   might violate the protocol, but avoids the potential for such characters to be used to simulate an
extra operation or parameter
-   , again causing
+    in that protocol, which might lead to
an unexpected and possibly harmful remote operation to be performed.
 
-   The use of URLs containing passwords that should be secret is clearly
-   unwise.
+   It is clearly unwise to use a URL that contains a password which is
+   intended to be secret. In particular, the use of a password within
+   the 'userinfo' component of a URL is strongly disrecommended except
+   in those rare cases where the 'password' parameter is intended to be
+   public.

!7.  Acknowledgements
!
!   This work is derived from concepts introduced by Tim Berners-Lee and
!   the World-Wide Web global information initiative.  Relative URLs are
!   described as "Partial URLs" in RFC 1630 [1].  That description was
!   expanded for inclusion as an appendix for an early draft of RFC 1738,
!   "Uniform Resource Locators (URL)" [2].  However, after further
!   discussion, the URI-WG decided to specify Relative URLs separately
!   from the primary URL draft.
!
!   This document is intended to fulfill the recommendations for Internet
!   Resource Locators as stated in [6].  It has benefited greatly from
!   the comments of all those participating in the URI-WG.  Particular
!   thanks go to Larry Masinter, Michael A. Dolan, Guido van Rossum, Dave
!   Kristol, David Robinson, and Brad Barber for identifying
!   problems/deficiencies in earlier drafts.
-7. Acknowledgements
+8. Acknowledgements
-
-   This paper builds on the basic WWW design (RFC 1630) and much
-   discussion of these issues by many people on the network. The
-   discussion was particularly stimulated by articles by Clifford Lynch,
-   Brewster Kahle [10] and Wengyik Yeong [18]. Contributions from John
-   Curran, Clifford Neuman, Ed Vielmetti and later the IETF URL BOF and
-   URI working group were incorporated.
-
-   Most recently, careful readings and comments by Dan Connolly, Ned
-   Freed, Roy Fielding, Guido van Rossum, Michael Dolan, Bert Bos, John
-   Kunze, Olle Jarnefors, Peter Svanberg and many others have helped
-   refine this RFC.

+   This document was derived from RFC 1738 [RFC1738] and RFC 1808
+   [RFC1808]; the acknowledgements in those specifications still apply.
+   In addition, contributions by Gisle Aas, Martin Beet, Martin Duerst,
+   Jim Gettys, Martijn Koster, Dave Kristol, Daniel LaLiberte, Foteos
+   Macrides, James Marshall, Ryan Moats, Keith Moore, and Lauren Wood
+   are gratefully acknowledged.
 
!8.  References
!
!   [1] Berners-Lee, T., "Universal Resource Identifiers in WWW: A
!       Unifying Syntax for the Expression of Names and Addresses of
!       Objects on the Network as used in the World-Wide Web", RFC 1630,
!       CERN, June 1994.
!
!   [2] Berners-Lee, T., Masinter, L., and M. McCahill, Editors, "Uniform
!       Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation,
!       University of Minnesota, December 1994.
!
!   [3] Berners-Lee T., and D. Connolly, "HyperText Markup Language
!       Specification -- 2.0", Work in Progress, MIT, HaL Computer
!       Systems, February 1995.
!       <URL:http://www.ics.uci.edu/pub/ietf/html/>
!
!   [4] Borenstein, N., and N. Freed, "MIME (Multipurpose Internet Mail
!       Extensions): Mechanisms for Specifying and Describing the Format
!       of Internet Message Bodies", RFC 1521, Bellcore, Innosoft,
!       September 1993.
!
!   [5] Crocker, D., "Standard for the Format of ARPA Internet Text
!       Messages", STD 11, RFC 822, UDEL, August 1982.

!   [6] Kunze, J., "Functional Recommendations for Internet Resource
!       Locators", RFC 1736, IS&T, UC Berkeley, February 1995.
-References
+9. References
-
-   [1] Anklesaria, F., McCahill, M., Lindner, P., Johnson, D.,
-       Torrey, D., and B. Alberti, "The Internet Gopher Protocol
-       (a distributed document search and retrieval protocol)",
-       RFC 1436, University of Minnesota, March 1993.
-       <URL:ftp://ds.internic.net/rfc/rfc1436.txt;type=a>
 -
-   [2] Anklesaria, F., Lindner, P., McCahill, M., Torrey, D.,
-       Johnson, D., and B. Alberti, "Gopher+: Upward compatible
-       enhancements to the Internet Gopher protocol",
-       University of Minnesota, July 1993.
-       <URL:ftp://boombox.micro.umn.edu/pub/gopher/gopher_protocol
-       /Gopher+/Gopher+.txt>
-

+   [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
+             Languages", BCP 18, RFC 2277, January 1998.
 
-   [3]
+   [RFC1630]
Berners-Lee, T., "Universal Resource Identifiers in WWW: A
Unifying Syntax for the Expression of Names and Addresses
of Objects on the Network as used in the World-Wide Web", RFC 1630,
-       CERN,
June 1994.
-       <URL:ftp://ds.internic.net/rfc/rfc1630.txt>
 
+   [RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, Editors,
+             "Uniform Resource Locators (URL)", RFC 1738, December 1994.
 
-
-   [4] Berners-Lee, T., "Hypertext Transfer Protocol (HTTP)",
-       CERN, November 1993.
-       <URL:ftp://info.cern.ch/pub/www/doc/http-spec.txt.Z>
-
+   [RFC1866] Berners-Lee T., and D. Connolly, "HyperText Markup Language
+             Specification -- 2.0", RFC 1866, November 1995.
 
-   [5]
+   [RFC1123]
Braden, R., Editor, "Requirements for Internet Hosts --
Application and Support", STD 3, RFC 1123, 
-IETF,
October 1989.
-       <URL:ftp://ds.internic.net/rfc/rfc1123.txt>
-
-   [6] Crocker, D. "Standard for the Format of ARPA Internet Text
-       Messages", STD 11, RFC 822, UDEL, April 1982.
-       <URL:ftp://ds.internic.net/rfc/rfc822.txt>
+   [RFC822]  Crocker, D., "Standard for the Format of ARPA Internet Text
+             Messages", STD 11, RFC 822, August 1982.
-
-   [7] Davis, F., Kahle, B., Morris, H., Salem, J., Shen, T., Wang, R.,
-       Sui, J., and M. Grinbaum, "WAIS Interface Protocol Prototype
-       Functional Specification", (v1.5), Thinking Machines
-       Corporation, April 1990.
-       <URL:ftp://quake.think.com/pub/wais/doc/protspec.txt>
-
-   [8] Horton, M. and R. Adams, "Standard For Interchange of USENET
-       Messages", RFC 1036, AT&T Bell Laboratories, Center for Seismic
-       Studies, December 1987.
-       <URL:ftp://ds.internic.net/rfc/rfc1036.txt>
-
-   [9] Huitema, C., "Naming: Strategies and Techniques", Computer
-       Networks and ISDN Systems 23 (1991) 107-110.
-
-  [10] Kahle, B., "Document Identifiers, or International Standard
-       Book Numbers for the Electronic Age", 1991.
-       <URL:ftp://quake.think.com/pub/wais/doc/doc-ids.txt>
-
-  [11] Kantor, B. and P. Lapsley, "Network News Transfer Protocol:
-       A Proposed Standard for the Stream-Based Transmission of News",
-       RFC 977, UC San Diego & UC Berkeley, February 1986.
-       <URL:ftp://ds.internic.net/rfc/rfc977.txt>

+   [RFC1808] Fielding, R., "Relative Uniform Resource Locators", RFC
+             1808, June 1995.
 
+   [RFC2046] Freed, N., and N. Borenstein, "Multipurpose Internet Mail
+             Extensions (MIME) Part Two: Media Types", RFC 2046,
+             November 1996.

-  [12] Kunze, J., "Functional Requirements for Internet Resource
-       Locators", Work in Progress, December 1994.
-       <URL:ftp://ds.internic.net/internet-drafts
-       /draft-ietf-uri-irl-fun-req-02.txt>
+   [RFC1736] Kunze, J., "Functional Recommendations for Internet
+             Resource Locators", RFC 1736, February 1995.
-
 
+   [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.
 
-  [13] Mockapetris, P., "Domain Names - Concepts and Facilities",
-       STD 13, RFC 1034, USC/Information Sciences Institute,
-       November 1987.
-       <URL:ftp://ds.internic.net/rfc/rfc1034.txt>
+   [RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities",
+             STD 13, RFC 1034, November 1987.
-
-  [14] Neuman, B., and S. Augart, "The Prospero Protocol",
-       USC/Information Sciences Institute, June 1993.
-       <URL:ftp://prospero.isi.edu/pub/prospero/doc
-       /prospero-protocol.PS.Z>
-
-  [15] Postel, J. and J. Reynolds, "File Transfer Protocol (FTP)",
-       STD 9, RFC 959, USC/Information Sciences Institute,
-       October 1985.
-       <URL:ftp://ds.internic.net/rfc/rfc959.txt>
 
+   [RFC2110] Palme, J., and A. Hopmann, "MIME E-mail Encapsulation of
+             Aggregate Documents, such as HTML (MHTML)", RFC 2110, March
+             1997.
 
-  [16]
+   [RFC1737]
Sollins, K., and L. Masinter, "Functional Requirements for
Uniform Resource Names", RFC 1737,
-MIT/LCS, Xerox Corporation,
December 1994.
-       <URL:ftp://ds.internic.net/rfc/rfc1737.txt>
-
-  [17] St. Pierre, M, Fullton, J., Gamiel, K., Goldman, J., Kahle, B.,
-       Kunze, J., Morris, H., and F. Schiettecatte, "WAIS over
-       Z39.50-1988", RFC 1625, WAIS, Inc., CNIDR, Thinking Machines
-       Corp., UC Berkeley, FS Consulting, June 1994.
-       <URL:ftp://ds.internic.net/rfc/rfc1625.txt>
-
-  [18] Yeong, W. "Towards Networked Information Retrieval", Technical
-       report 91-06-25-01, Performance Systems International, Inc.
-       <URL:ftp://uu.psi.com/wp/nir.txt>, June 1991.
-
-  [19] Yeong, W., "Representing Public Archives in the Directory",
-       Work in Progress, November 1991.

-  [20]
+   [ASCII]   US-ASCII.
"Coded Character Set -- 7-bit American Standard
Code for Information Interchange", ANSI X3.4-1986.
 
+   [UTF-8]   Yergeau, F., "UTF-8, a transformation format of ISO 10646",
+             RFC 2279, January 1998.
 
-Editors' Addresses
!9.  Author's Address
+10. Authors' Addresses
 
Tim Berners-Lee
-World-Wide Web project
+   World Wide Web Consortium
-CERN,
+   MIT Laboratory for Computer Science, NE43-356
-1211 Geneva 23,
-Switzerland
+   545 Technology Square
+   Cambridge, MA 02139
 
-Phone: +41 (22)767 3755
-Fax: +41 (22)767 7155
-EMail: timbl@info.cern.ch
+   Fax: +1(617)258-8682
+   EMail: timbl@w3.org

Roy T. Fielding
Department of Information and Computer Science
!   University of California
+   University of California, Irvine
!   Irvine, CA  92717-3425
+   Irvine, CA  92697-3425
!   U.S.A.
 
!   Tel: +1 (714) 824-4049
!   Fax: +1 (714) 824-4056
+   Fax: +1(949)824-1715
EMail: fielding@ics.uci.edu

Larry Masinter
Xerox PARC
3333 Coyote Hill Road
Palo Alto, CA 94034
 
-Phone: (415) 812-4365
-Fax: (415) 812-4333
+   Fax: +1(415)812-4333
EMail: masinter@parc.xerox.com

-Mark McCahill
-Computer and Information Services,
-University of Minnesota
-Room 152 Shepherd Labs
-100 Union Street SE
-Minneapolis, MN 55455
-
-Phone: (612) 625 1300
-EMail: mpm@boombox.micro.umn.edu

+A. Collected BNF for URI
 
-; The generic form of a URL is:
+      URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
-genericurl     = scheme ":" schemepart
+      absoluteURI   = scheme ":" ( hier_part | opaque_part )
+      relativeURI   = ( net_path | abs_path | rel_path ) [ "?" query ]
+
-schemepart     = *xchar | ip-schemepart
+      hier_part     = ( net_path | abs_path ) [ "?" query ]
+      opaque_part   = uric_no_slash *uric
+
+      uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
+                      "&" | "=" | "+" | "$" | ","
+
-; URL schemeparts for ip based protocols:
-ip-schemepart  = "//" login [ "/" urlpath ]
+      net_path      = "//" authority [ abs_path ]
+      abs_path      = "/"  path_segments
+      rel_path      = rel_segment [ abs_path ]
+
+      rel_segment   = 1*( unreserved | escaped |
+                          ";" | "@" | "&" | "=" | "+" | "$" | "," )
+
-; the scheme is in lower case; interpreters should use case-ignore
-scheme         = 1*[ lowalpha | digit | "+" | "-" | "." ]
+      scheme        = alpha *( alpha | digit | "+" | "-" | "." )
+
+      authority     = server | reg_name
+
+      reg_name      = 1*( unreserved | escaped | "$" | "," |
+                          ";" | ":" | "@" | "&" | "=" | "+" )
+
-login          = [ user [ ":" password ] "@" ] hostport
+      server        = [ [ userinfo "@" ] hostport ]
-user           = *[ uchar | ";" | "?" | "&" | "=" ]
+      userinfo      = *( unreserved | escaped |
+                         ";" | ":" | "&" | "=" | "+" | "$" | "," )
-password       = *[ uchar | ";" | "?" | "&" | "=" ]
+

hostport      = host [ ":" port ]
-host           = hostname | hostnumber
+      host          = hostname | IPv4address
-hostname       = *[ domainlabel "." ] toplabel
+      hostname      = *( domainlabel "." ) toplabel [ "." ]
-domainlabel    = alphadigit | alphadigit *[ alphadigit | "-" ] alphadigit
+      domainlabel   = alphanum | alphanum *( alphanum | "-" ) alphanum
-toplabel       = alpha | alpha *[ alphadigit | "-" ] alphadigit
+      toplabel      = alpha | alpha *( alphanum | "-" ) alphanum
-hostnumber     = digits "." digits "." digits "." digits
+      IPv4address   = 1*digit "." 1*digit "." 1*digit "." 1*digit
-port           = digits
+      port          = *digit
+
+      path          = [ abs_path | opaque_part ]
+      path_segments = segment *( "/" segment )
+      segment       = *pchar *( ";" param )
+      param         = *pchar
-urlpath        = *xchar    ; depends on protocol see section 3.1
+      pchar         = unreserved | escaped |
+                      ":" | "@" | "&" | "=" | "+" | "$" | ","
+
+      query         = *uric
+
+      fragment      = *uric
+
+      uric          = reserved | unreserved | escaped
+      reserved      = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
+                      "$" | ","
+      unreserved    = alphanum | mark
+      mark          = "-" | "_" | "." | "!" | "~" | "*" | "'" |
+                      "(" | ")"
+
+      escaped       = "%" hex hex
+      hex           = digit | "A" | "B" | "C" | "D" | "E" | "F" |
+                              "a" | "b" | "c" | "d" | "e" | "f"
+
-alphadigit     = alpha | digit
+      alphanum      = alpha | digit
+      alpha         = lowalpha | upalpha
+


-; Specific predefined schemes are defined here; new schemes
-; may be registered with IANA
-url            = httpurl | ftpurl | newsurl |
-                 nntpurl | telneturl | gopherurl |
-                 waisurl | mailtourl | fileurl |
-                 prosperourl | otherurl
-; new schemes follow the general syntax
-otherurl       = genericurl
-; The predefined schemes:
-; FTP (see also RFC959)
-ftpurl         = "ftp://" login [ "/" fpath [ ";type=" ftptype ]]
-fpath          = fsegment *[ "/" fsegment ]
-fsegment       = *[ uchar | "?" | ":" | "@" | "&" | "=" ]
-ftptype        = "A" | "I" | "D" | "a" | "i" | "d"
-; FILE
-fileurl        = "file://" [ host | "localhost" ] "/" fpath
-; HTTP
-httpurl        = "http://" hostport [ "/" hpath [ "?" search ]]
-hpath          = hsegment *[ "/" hsegment ]
-hsegment       = *[ uchar | ";" | ":" | "@" | "&" | "=" ]
-search         = *[ uchar | ";" | ":" | "@" | "&" | "=" ]
-; GOPHER (see also RFC1436)
-gopherurl      = "gopher://" hostport [ / [ gtype [ selector
-                 [ "%09" search [ "%09" gopher+_string ] ] ] ] ]
-gtype          = xchar
-selector       = *xchar
-gopher+_string = *xchar
-; MAILTO (see also RFC822)
-mailtourl      = "mailto:" encoded822addr
-encoded822addr = 1*xchar               ; further defined in RFC822
-; NEWS (see also RFC1036)
-newsurl        = "news:" grouppart
-grouppart      = "*" | group | article
-group          = alpha *[ alpha | digit | "-" | "." | "+" | "_" ]
-article        = 1*[ uchar | ";" | "/" | "?" | ":" | "&" | "=" ] "@" host
-; NNTP (see also RFC977)
-nntpurl        = "nntp://" hostport "/" group [ "/" digits ]
-; TELNET
-telneturl      = "telnet://" login [ "/" ]
-; WAIS (see also RFC1625)
-waisurl        = waisdatabase | waisindex | waisdoc
-waisdatabase   = "wais://" hostport "/" database
-waisindex      = "wais://" hostport "/" database "?" search
-waisdoc        = "wais://" hostport "/" database "/" wtype "/" wpath
-database       = *uchar
-wtype          = *uchar
-wpath          = *uchar
 
-; PROSPERO


-prosperourl    = "prospero://" hostport "/" ppath *[ fieldspec ]
-ppath          = psegment *[ "/" psegment ]
-psegment       = *[ uchar | "?" | ":" | "@" | "&" | "=" ]
-fieldspec      = ";" fieldname "=" fieldvalue
-fieldname      = *[ uchar | "?" | ":" | "@" | "&" ]
-fieldvalue     = *[ uchar | "?" | ":" | "@" | "&" ]

-; Miscellaneous definitions

lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
-hialpha        = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
+      upalpha  = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
                  "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
                  "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"

-alpha          = lowalpha | hialpha
digit    = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
-safe           = "$" | "-" | "_" | "." | "+"
-extra          = "!" | "*" | "'" | "(" | ")" | ","
-national       = "{" | "}" | "|" | "\" | "^" | "~" | "[" | "]" | "`"
-punctuation    = "<" | ">" | "#" | "%" | <">
-
-
-reserved       = ";" | "/" | "?" | ":" | "@" | "&" | "="
-hex            = digit | "A" | "B" | "C" | "D" | "E" | "F" |
-                 "a" | "b" | "c" | "d" | "e" | "f"
-escape         = "%" hex hex
-
-unreserved     = alpha | digit | safe | extra
-uchar          = unreserved | escape
-xchar          = unreserved | reserved | escape
-digits         = 1*digit

+B. Parsing a URI Reference with a Regular Expression
+
+   As described in Section 4.3, the generic URI syntax is not sufficient
+   to disambiguate the components of some forms of URI.  Since the
+   "greedy algorithm" described in that section is identical to the
+   disambiguation method used by POSIX regular expressions, it is
+   natural and commonplace to use a regular expression for parsing the
+   potential four components and fragment identifier of a URI reference.
+
+   The following line is the regular expression for breaking-down a URI
+   reference into its components.
+
+      ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
+       12            3  4          5       6  7        8 9
+
+   The numbers in the second line above are only to assist readability;
+   they indicate the reference points for each subexpression (i.e., each
+   paired parenthesis).  We refer to the value matched for subexpression
+   <n> as $<n>.  For example, matching the above expression to
+
+      http://www.ics.uci.edu/pub/ietf/uri/#Related
+
+   results in the following subexpression matches:
+
+      $1 = http:
+      $2 = http
+      $3 = //www.ics.uci.edu
+      $4 = www.ics.uci.edu
+      $5 = /pub/ietf/uri/
+      $6 = <undefined>
+      $7 = <undefined>
+      $8 = #Related
+      $9 = Related
+
+   where <undefined> indicates that the component is not present, as is
+   the case for the query component in the above example.  Therefore, we
+   can determine the value of the four components and fragment as
+
+      scheme    = $2
+      authority = $4
+      path      = $5
+      query     = $7
+      fragment  = $9
+
+   and, going in the opposite direction, we can recreate a URI reference
+   from its components using the algorithm in step 7 of Section 5.2.
+
!5.  Examples and Recommended Practice
+C. Examples of Resolving Relative URI References
+
!   Within an object with a well-defined base URL of
+   Within an object with a well-defined base URI of
+
!      Base: <URL:http://a/b/c/d;p?q#f>
+      http://a/b/c/d;p?q

!   the relative URLs would be resolved as follows:
+   the relative URI would be resolved as follows:
+
!5.1.  Normal Examples
+C.1.  Normal Examples

!      g:h        = <URL:g:h>
!      g          = <URL:http://a/b/c/g>
!      ./g        = <URL:http://a/b/c/g>
!      g/         = <URL:http://a/b/c/g/>
!      /g         = <URL:http://a/g>
!      //g        = <URL:http://g>
+      g:h           =  g:h
+      g             =  http://a/b/c/g
+      ./g           =  http://a/b/c/g
+      g/            =  http://a/b/c/g/
+      /g            =  http://a/g
+      //g           =  http://g
!      ?y         = <URL:http://a/b/c/d;p?y>
+      ?y            =  http://a/b/c/?y
!      g?y        = <URL:http://a/b/c/g?y>
+      g?y           =  http://a/b/c/g?y
!      g?y/./x    = <URL:http://a/b/c/g?y/./x>
!      #s         = <URL:http://a/b/c/d;p?q#s>
+      #s            =  (current document)#s
!      g#s        = <URL:http://a/b/c/g#s>
+      g#s           =  http://a/b/c/g#s
!      g#s/./x    = <URL:http://a/b/c/g#s/./x>
!      g?y#s      = <URL:http://a/b/c/g?y#s>
+      g?y#s         =  http://a/b/c/g?y#s
!      ;x         = <URL:http://a/b/c/d;x>
+      ;x            =  http://a/b/c/;x
!      g;x        = <URL:http://a/b/c/g;x>
+      g;x           =  http://a/b/c/g;x
!      g;x?y#s    = <URL:http://a/b/c/g;x?y#s>
+      g;x?y#s       =  http://a/b/c/g;x?y#s
!      .          = <URL:http://a/b/c/>
!      ./         = <URL:http://a/b/c/>
!      ..         = <URL:http://a/b/>
!      ../        = <URL:http://a/b/>
!      ../g       = <URL:http://a/b/g>
!      ../..      = <URL:http://a/>
!      ../../     = <URL:http://a/>
!      ../../g    = <URL:http://a/g>
+      .             =  http://a/b/c/
+      ./            =  http://a/b/c/
+      ..            =  http://a/b/
+      ../           =  http://a/b/
+      ../g          =  http://a/b/g
+      ../..         =  http://a/
+      ../../        =  http://a/
+      ../../g       =  http://a/g
+

!5.2.  Abnormal Examples
+C.2.  Abnormal Examples
 
    Although the following abnormal examples are unlikely to occur in
!   normal practice, all URL parsers should be capable of resolving them
+   normal practice, all URI parsers should be capable of resolving them
    consistently.  Each example uses the same base as above.
 
!   An empty reference resolves to the complete base URL:
+   An empty reference refers to the start of the current document.
 
!      <>            = <URL:http://a/b/c/d;p?q#f>
+      <>            =  (current document)
 
    Parsers must be careful in handling the case where there are more
    relative path ".." segments than there are hierarchical levels in the
!   base URL's path.  Note that the ".." syntax cannot be used to change
+   base URI's path.  Note that the ".." syntax cannot be used to change
!   the <net_loc> of a URL.
+   the authority component of a URI.
 
!      ../../../g    = <URL:http://a/../g>
!      ../../../../g = <URL:http://a/../../g>
+      ../../../g    =  http://a/../g
+      ../../../../g =  http://a/../../g
+
+   In practice, some implementations strip leading relative symbolic
+   elements (".", "..") after applying a relative URI calculation, based
+   on the theory that compensating for obvious author errors is better
+   than allowing the request to fail.  Thus, the above two references
+   will be interpreted as "http://a/g" by some implementations.
 
    Similarly, parsers must avoid treating "." and ".." as special when
    they are not complete components of a relative path.
 
!      /./g          = <URL:http://a/./g>
!      /../g         = <URL:http://a/../g>
!      g.            = <URL:http://a/b/c/g.>
!      .g            = <URL:http://a/b/c/.g>
!      g..           = <URL:http://a/b/c/g..>
!      ..g           = <URL:http://a/b/c/..g>
+      /./g          =  http://a/./g
+      /../g         =  http://a/../g
+      g.            =  http://a/b/c/g.
+      .g            =  http://a/b/c/.g
+      g..           =  http://a/b/c/g..
+      ..g           =  http://a/b/c/..g
 
!   Less likely are cases where the relative URL uses unnecessary or
+   Less likely are cases where the relative URI uses unnecessary or
    nonsensical forms of the "." and ".." complete path segments.
 
!      ./../g        = <URL:http://a/b/g>
!      ./g/.         = <URL:http://a/b/c/g/>
!      g/./h         = <URL:http://a/b/c/g/h>
!      g/../h        = <URL:http://a/b/c/h>
+      ./../g        =  http://a/b/g
+      ./g/.         =  http://a/b/c/g/
+      g/./h         =  http://a/b/c/g/h
+      g/../h        =  http://a/b/c/h
+      g;x=1/./y     =  http://a/b/c/g;x=1/y
+      g;x=1/../y    =  http://a/b/c/y
+
+   All client applications remove the query component from the base URI
+   before resolving relative URI.  However, some applications fail to
+   separate the reference's query and/or fragment components from a
+   relative path before merging it with the base path.  This error is
+   rarely noticed, since typical usage of a fragment never includes the
+   hierarchy ("/") character, and the query component is not normally
+   used within relative references.
+
+      g?y/./x       =  http://a/b/c/g?y/./x
+      g?y/../x      =  http://a/b/c/g?y/../x
+      g#s/./x       =  http://a/b/c/g#s/./x
+      g#s/../x      =  http://a/b/c/g#s/../x
+
!
!   Finally, some older parsers allow the scheme name to be present in a relative URL
+   Some parsers allow the scheme name to be present in a relative URI
!   if it is the same as the base URL scheme.  This is considered to be a
+   if it is the same as the base URI scheme.  This is considered to be a
!   loophole in prior specifications of partial URLs
+   loophole in prior specifications of partial URI [RFC1630].
!   [1] and should be avoided by future parsers.
+   Its use should be avoided.

!      http:g        = <URL:http:g>
!      http:         = <URL:http:>
+      http:g        =  http:g           ; for validating parsers
+                    |  http://a/b/c/g   ; for backwards compatibility
!
!5.3.  Recommended Practice
!
!   Authors should be aware that path names which contain a colon ":"
!   character cannot be used as the first component of a relative URL
!   path (e.g., "this:that") because they will likely be mistaken for a
!   scheme name.  It is therefore necessary to precede such cases with
!   other components (e.g., "./this:that"), or to escape the colon
!   character (e.g., "this%3Athat"), in order for them to be correctly
!   parsed.  The former solution is preferred because it does not affect
!   the absolute form of the URL.
!
!   There is an ambiguity in the semantics for the ftp URL scheme
!   regarding the use of a trailing slash ("/") character and/or a
!   parameter ";type=d" to indicate a resource that is an ftp directory.
!   If the result of retrieving that directory includes embedded relative
!   URLs, it is necessary that the base URL path for that result include
!   a trailing slash.  For this reason, we recommend that the ";type=d"
!   parameter value not be used within contexts that allow relative URLs.
+
!10.  Appendix - Embedding the Base URL in HTML documents
+D. Embedding the Base URI in HTML documents
!
!   It is useful to consider an example of how the base URL of a document
+   It is useful to consider an example of how the base URI of a document
    can be embedded within the document's content.  In this appendix, we
    describe how documents written in the Hypertext Markup Language
!   (HTML) [3] can include an embedded base URL.  This appendix does not
+   (HTML) [RFC1866] can include an embedded base URI.  This appendix
!   form a part of the relative URL specification and should not be
+   does not form a part of the URI specification and should not be
    considered as anything more than a descriptive example.
 
    HTML defines a special element "BASE" which, when present in the
    "HEAD" portion of a document, signals that the parser should use the
!   BASE element's "HREF" attribute as the base URL for resolving any
+   BASE element's "HREF" attribute as the base URI for resolving any
!   relative URLs.  The "HREF" attribute must be an absolute URL.  Note
+   relative URI.  The "HREF" attribute must be an absolute URI.  Note
    that, in HTML, element and attribute names are case-insensitive.  For
    example:

+      <!doctype html public "-//IETF//DTD HTML//EN">
+      <HTML><HEAD>
+      <TITLE>An example HTML document</TITLE>
+      <BASE href="http://www.ics.uci.edu/Test/a/b/c">
+      </HEAD><BODY>
+      ... <A href="../x">a hypertext anchor</A> ...
+      </BODY></HTML>
+
    A parser reading the example document should interpret the given
!   relative URL "../x" as representing the absolute URL
+   relative URI "../x" as representing the absolute URI
 
!      <URL:http://www.ics.uci.edu/Test/a/x>
+      <http://www.ics.uci.edu/Test/a/x>
+
!+   regardless of the context in which the example document was obtained.
+
-APPENDIX: Recommendations for URLs in Context
+E. Recommendations for Delimiting URI in Context

-   URIs, including URLs, are intended to be transmitted through
-   protocols which provide a context for their interpretation.
+   URI are often transmitted through formats that do not provide a clear
+   context for their interpretation.  For example, there are many
+   occasions when URI are included in plain text; examples include text
+   sent in electronic mail, USENET news messages, and, most importantly,
+   printed on paper.  In such cases, it is important to be able to
+   delimit the URI from the rest of the text, and in particular from
+   punctuation marks that might be mistaken for part of the URI.
-
-   In some cases, it will be necessary to distinguish URLs from other
-   possible data structures in a syntactic structure. In this case, is
-   recommended that URLs be preceeded with a prefix consisting of the
-   characters "URL:". For example, this prefix may be used to
-   distinguish URLs from other kinds of URIs.
-
-   In addition, there are many occasions when URLs are included in other
-   kinds of text; examples include electronic mail, USENET news
-   messages, or printed on paper. In such cases, it is convenient to
-   have a separate syntactic wrapper that delimits the URL and separates
-   it from the rest of the text, and in particular from punctuation
-   marks that might be mistaken for part of the URL. For this purpose,
-   is recommended that angle brackets ("<" and ">"), along with the
-   prefix "URL:", be used to delimit the boundaries of the URL.  This
-   wrapper does not form part of the URL and should not be used in
-   contexts in which delimiters are already specified.
+
+   In practice, URI are delimited in a variety of ways, but usually
+   within double-quotes "http://test.com/", angle brackets
+   <http://test.com/>, or just using whitespace
+
+                             http://test.com/
+
+   These wrappers do not form part of the URI.
-
-   In the case where a fragment
-/anchor
identifier is associated with a
+URI reference, the fragment
-   URL (following a "#"), the identifier
would be placed within the brackets as well
+   (separated from the URI with a "#" character)
.

    In some cases, extra whitespace (spaces, linebreaks, tabs, etc.) may need to be added to break long
-   URLs
+  URI
-  across lines.  The whitespace
+ across lines. The whitespace
should be ignored when extracting the
- URL.
+URI.
 
    No whitespace should be introduced after a hyphen ("-") character.
    Because some typesetters and printers may (erroneously) introduce a
    hyphen at the end of line when breaking a line, the interpreter of a
-   URL
+   URI
containing a line break immediately after a hyphen should ignore
all unescaped whitespace around the line break, and should be aware
that the hyphen may or may not actually be part of the
-    URL.
+    URI.
+
+   Using <> angle brackets around each URI is especially recommended as
+   a delimiting style for URI that contain whitespace.
+
+   The prefix "URL:" (with or without a trailing space) was recommended
+   as a way to used to help distinguish a URL from other bracketed
+   designators, although this is not common in practice.
+
+   For robustness, software that accepts user-typed URI should attempt
+   to recognize and strip both delimiters and embedded whitespace.

-   Examples:
+   For example, the text:
-
-      Yes, Jim, I found it under <URL:ftp://info.cern.ch/pub/www/doc;
-      type=d> but you can probably pick it up from <URL:ftp://ds.in
-      ternic.net/rfc>.  Note the warning in <URL:http://ds.internic.
-      net/instructions/overview.html#WARNING>.

+      Yes, Jim, I found it under "http://www.w3.org/Addressing/",
+      but you can probably pick it up from <ftp://ds.internic.
+      net/rfc/>.  Note the warning in <http://www.ics.uci.edu/pub/
+      ietf/uri/historical.html#WARNING>.
+
+   contains the URI references
+
+      http://www.w3.org/Addressing/
+      ftp://ds.internic.net/rfc/
+      http://www.ics.uci.edu/pub/ietf/uri/historical.html#WARNING
+
+F. Abbreviated URLs
+
+   The URL syntax was designed for unambiguous reference to network
+   resources and extensibility via the URL scheme.  However, as URL
+   identification and usage have become commonplace, traditional media
+   (television, radio, newspapers, billboards, etc.) have increasingly
+   used abbreviated URL references.  That is, a reference consisting of
+   only the authority and path portions of the identified resource, such
+   as
+
+      www.w3.org/Addressing/
+
+   or simply the DNS hostname on its own.  Such references are primarily
+   intended for human interpretation rather than machine, with the
+   assumption that context-based heuristics are sufficient to complete
+   the URL (e.g., most hostnames beginning with "www" are likely to have
+   a URL prefix of "http://").  Although there is no standard set of
+   heuristics for disambiguating abbreviated URL references, many client
+   implementations allow them to be entered by the user and
+   heuristically resolved.  It should be noted that such heuristics may
+   change over time, particularly when new URL schemes are introduced.
+
+   Since an abbreviated URL has the same syntax as a relative URL path,
+   abbreviated URL references cannot be used in contexts where relative
+   URLs are expected.  This limits the use of abbreviated URLs to places
+   where there is no defined base URL, such as dialog boxes and off-line
+   advertisements.

-
+G. Summary of Non-editorial Changes
+
+G.1. Additions
+
+   Section 4 (URI References) was added to stem the confusion regarding
+   "what is a URI" and how to describe fragment identifiers given that
+   they are not part of the URI, but are part of the URI syntax and
+   parsing concerns.  In addition, it provides a reference definition
+   for use by other IETF specifications (HTML, HTTP, etc.) that have
+   previously attempted to redefine the URI syntax in order to account
+   for the presence of fragment identifiers in URI references.
+
+   Section 2.4 was rewritten to clarify a number of misinterpretations
+   and to leave room for fully internationalized URI.
+
+   Appendix F on abbreviated URLs was added to describe the shortened
+   references often seen on television and magazine advertisements and
+   explain why they are not used in other contexts.
+
+G.2. Modifications from both RFC 1738 and RFC 1808
+
+   Changed to URI syntax instead of just URL.
+
+   Confusion regarding the terms "character encoding", the URI
+   "character set", and the escaping of characters with %<hex><hex>
+   equivalents has (hopefully) been reduced.  Many of the BNF rule names
+   regarding the character sets have been changed to more accurately
+   describe their purpose and to encompass all "characters" rather than
+   just US-ASCII octets.  Unless otherwise noted here, these
+   modifications do not affect the URI syntax.
+
+   Both RFC 1738 and RFC 1808 refer to the "reserved" set of characters
+   as if URI-interpreting software were limited to a single set of
+   characters with a reserved purpose (i.e., as meaning something other
+   than the data to which the characters correspond), and that this set
+   was fixed by the URI scheme.  However, this has not been true in
+   practice; any character that is interpreted differently when it is
+   escaped is, in effect, reserved.  Furthermore, the interpreting
+   engine on a HTTP server is often dependent on the resource, not just
+   the URI scheme.  The description of reserved characters has been
+   changed accordingly.
+
+   The plus "+", dollar "$", and comma "," characters have been added to
+   those in the "reserved" set, since they are treated as reserved
+   within the query component.
+
+   The tilde "~" character was added to those in the "unreserved" set,
+   since it is extensively used on the Internet in spite of the
+   difficulty to transcribe it with some keyboards.
+
+   The syntax for URI scheme has been changed to require that all
+   schemes begin with an alpha character.
+
+   The "user:password" form in the previous BNF was changed to a
+   "userinfo" token, and the possibility that it might be
+   "user:password" made scheme specific. In particular, the use of
+   passwords in the clear is not even suggested by the syntax.
+
+   The question-mark "?" character was removed from the set of allowed
+   characters for the userinfo in the authority component, since testing
+   showed that many applications treat it as reserved for separating the
+   query component from the rest of the URI.
+
+   The semicolon ";" character was added to those stated as being
+   reserved within the authority component, since several new schemes
+   are using it as a separator within userinfo to indicate the type of
+   user authentication.
+
+   RFC 1738 specified that the path was separated from the authority
+   portion of a URI by a slash.  RFC 1808 followed suit, but with a
+   fudge of carrying around the separator as a "prefix" in order to
+   describe the parsing algorithm.  RFC 1630 never had this problem,
+   since it considered the slash to be part of the path.  In writing
+   this specification, it was found to be impossible to accurately
+   describe and retain the difference between the two URI
+      <foo:/bar>   and   <foo:bar>
+   without either considering the slash to be part of the path (as
+   corresponds to actual practice) or creating a separate component just
+   to hold that slash.  We chose the former.
+
+G.3. Modifications from RFC 1738
+
+   The definition of specific URL schemes and their scheme-specific
+   syntax and semantics has been moved to separate documents.
+
+   The URL host was defined as a fully-qualified domain name.  However,
+   many URLs are used without fully-qualified domain names (in contexts
+   for which the full qualification is not necessary), without any host
+   (as in some file URLs), or with a host of "localhost".
+
+   The URL port is now *digit instead of 1*digit, since systems are
+   expected to handle the case where the ":" separator between host and
+   port is supplied without a port.
+
+   The recommendations for delimiting URI in context (Appendix E) have
+   been adjusted to reflect current practice.
+
+G.4. Modifications from RFC 1808
+
+   RFC 1808 (Section 4) defined an empty URL reference (a reference
+   containing nothing aside from the fragment identifier) as being a
+   reference to the base URL.  Unfortunately, that definition could be
+   interpreted, upon selection of such a reference, as a new retrieval
+   action on that resource.  Since the normal intent of such references
+   is for the user agent to change its view of the current document to
+   the beginning of the specified fragment within that document, not to
+   make an additional request of the resource, a description of how to
+   correctly interpret an empty reference has been added in Section 4.
+
+   The description of the mythical Base header field has been replaced
+   with a reference to the Content-Location header field defined by
+   MHTML [RFC2110].
+
+   RFC 1808 described various schemes as either having or not having the
+   properties of the generic URI syntax.  However, the only requirement
+   is that the particular document containing the relative references
+   have a base URI that abides by the generic URI syntax, regardless of
+   the URI scheme, so the associated description has been updated to
+   reflect that.
+
+   The BNF term <net_loc> has been replaced with <authority>, since the
+   latter more accurately describes its use and purpose.  Likewise, the
+   authority is no longer restricted to the IP server syntax.
+
+   Extensive testing of current client applications demonstrated that
+   the majority of deployed systems do not use the ";" character to
+   indicate trailing parameter information, and that the presence of a
+   semicolon in a path segment does not affect the relative parsing of
+   that segment.  Therefore, parameters have been removed as a separate
+   component and may now appear in any path segment.  Their influence
+   has been removed from the algorithm for resolving a relative URI
+   reference.  The resolution examples in Appendix C have been modified
+   to reflect this change.
+
+   Implementations are now allowed to work around misformed relative
+   references that are prefixed by the same scheme as the base URI, but
+   only for schemes known to use the <hier_part> syntax.
+
+H.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (1998).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
