2004/id/draft-ietf-uri-url-irp-04.txt


IETF URI Working Group                                        R. Denenberg
Internet-Draft                                                J. Kunze
draft-ietf-uri-url-irp-04.txt                                 D. Lynch
5 February 1996                                               Editors
Expires in six months

                  Uniform Resource Locators for Z39.50


1. Status of this Document

This document is an Internet-Draft.  Internet-Drafts are working documents
of the Internet Engineering Task Force (IETF), its Areas, and its Working
Groups.  Note that other groups may also distribute working documents as
Internet-Drafts.

Internet-Drafts are working documents valid for a maximum of six months.
Internet-Drafts may be updated, replaced, or obsoleted by other documents
at any time.  It is not appropriate to use Internet-Drafts as reference
material or to cite them other than as a ``working draft' or ``work in
progress.''

To learn the current status of any Internet-Draft, please check the
1id-abstracts.txt listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
munnari.oz.au.

Distribution of this document is unlimited.  Please send comments to
jak@violet.berkeley.edu, or to the discussion lists uri@bunyip.com and
z3950iw@nervm.nerdc.ufl.edu.


2. Introduction

Z39.50 is an information retrieval protocol that does not fit neatly into
a retrieval model designed primarily around the stateless fetch of data.
Instead, it models a general user inquiry as a session-oriented, multi-
step task, any step of which may be suspended temporarily while the
server requests additional parameters from the client before continuing.
Some, none, or all of these client/server interactions may require
participation of the client user, depending only on the client software
(the protocol itself makes no such requirements).

On the other hand, retrieval of "well-known" data may be performed in
a single step, that is, with a degenerate Z39.50 session consisting of
exactly one protocol search request and response.  Besides the basic
search sub-service, there are several ancillary sub-services (e.g., Scan,
Result Set Delete).  Among the functions covered by combinations of the
sub-services, two core functions emerge as appropriately handled by two
separate URL schemes:  the Session URL and the Retrieval URL.

Using two schemes instead of one makes a critical distinction between a
Z39.50 Session URL, which opens a client session initialized for
interactive use by the user, and a Z39.50 Retrieval URL, which opens and
closes a client session to retrieve a specific information item.  Making
this distinction at the scheme level allows the user interface to reflect
it on to the user, without requiring the user interface to parse otherwise
opaque parts of the URL (consistent with current practice).   


3. The Z39.50 Session URL

The Z39.50 Session URL may be informally described as providing the 
mechanism to switch the user to a Z39.50 client application. 

   -  Host is required.
   -  Port is optional, and defaults to 210.
   -  All other parameters are optional.
   -  The Z39.50 client will start a session to the specified host/port
      (alternatively, it need not explicitly start a session, but may
      instead utilize an already open session to the same host/port).
   -  A database must be included if docid is included.
   -  If docid is included, the client will perform the specified search
      (in the same manner as for the retrieval URL, specified below).
   -  If docid is not included, and other parameters (besides host/port)
      are specified, the client may use those parameters as "hints".
      Various clients may choose to treat them as requirements, or as
      preferences, or ignore them.
   -  In any case (whether a search is performed or not), the client will
      leave the Z39.50 session open for the user, to do retrievals, new
      searches, etc.  (This is the main distinction from the Retrieval URL 
      which leaves it up to the client whether or not to keep the Z39.50 
      session open.)


4. The Z39.50 Retrieval URL

The Z39.50 Retrieval URL is intended to allow a Z39.50 session to be used as
a transparent transfer mechanism to retrieve a specific information object.
A Z39.50 client uses information in the URL to formulate a Search Request.
The server's Search Response indicates how many records match the Request.
If the number of matching records does not equal one, the retrieval is
considered unsuccessful, and the client application's behavior is not defined.
If the number of matching records equals one, the server may have included
the desired record in the Search Response.  If not, the client requests
transmission of the record with a Present Request.  After the client has
received the specified record it may close the Z39.50 session immediately,
or keep it open for subsequent retrievals.    

   -  Host is required.
   -  Port is optional, and defaults to 210.
   -  A database is required.
   -  The meaning of a retrieval URL with no docid is undefined.
   -  The docid is placed into a type-1 query, as the single term, in
      the general format (tag 45), using the Bib-1 attribute set, with
      a Use attribute value of docid, and a structure attribute of URx.
      The docid string is server-defined and completely opaque to the client.
   -  If element set name (esn) is not specified, it is the client's choice.
      If esn is specified, it should be used either in the Search
      request for the value of small- and/or medium- set-element-set-names
      or in a Present request following a Search.  These terms and their
      use are defined within the Z39.50 Standard [2].
   -  If record syntax (rs) is not specified, it is the client's choice.
      If one or more record syntaxes are specified, the client should select
      one (preferably the first in the list that it supports) and use it in
      a Search or Present request as the value of PreferredRecordSyntax.


5. BNF for Z39.50 URLs

The Z39.50 Session and Retrieval URLs follow the Common Internet Scheme
Syntax as defined in RFC 1738, "Uniform Resource Locators (URL)" [1].
In the definition, literals are quoted with "", optional elements
are enclosed in [brackets], "|" is used to designate alternatives,
and elements may be preceded with <n>* to designate n or more
repetitions of the following element; n defaults to 0.  

z39.50url      = zscheme "://" host [":" port]
                      ["/" [database *["+" database]
                             ["?" docid]]
                           [";esn=" elementset]
                           [";rs=" recordsyntax *[ "+" recordsyntax]]]

zscheme        = "z39.50r" | "z39.50s"
database       = uchar
docid          = uchar
elementset     = uchar
recordsyntax   = uchar

Future extensions to these URLs will be of the form of [;keyword=value].

The following definitions are from RFC 1738. Between the Internet Draft
version and RFC 1738 two relevant changes were made: '=' was moved from
the <extra> character class to <reserved>, and <national> was removed from
the alternatives in <unreserved>. Neither <national> nor <punctuation> is
referred to in this document nor in RFC 1738.

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" |
                 "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

6. Security Considerations

The two Z39.50 URL schemes are subject to the same security implications
as the general URL scheme [1], so the usual precautions apply.  This means,
for example, that a locator might no longer point to the object that was
originally intended.  It also means that it may be possible to construct
a URL so that an attempt to perform a harmless idempotent operation such
as the retrieval of an object will in fact cause a possibly damaging
remote operation to occur.


7. Acknowledgements

The Z39.50 Implementors Group contributed the substance of this document.


8. References

   [1] Berners-Lee, T., Masinter, L., McCahill, M. (editors), "Uniform
       Resource Locators (URL)", RFC 1738, December 1994.
       ftp://ds.internic.net/rfc/rfc1738.txt

   [2] ANSI/NISO Z39.50-1994, "ANSI Z39.50:  Information Retrieval Service
       and Protocol", 1994.  ftp://ftp.loc.gov/pub/z3950/

   [3] ANSI/NISO Z39.50-1992, "ANSI Z39.50:  Information Retrieval Service
       and Protocol", 1992.
       ftp://ftp.cni.org/pub/NISO/docs/Z39.50-1992/www/Z39.50.toc.html
       (also available in hard copy from Omnicom Information Service,
       115 Park St., SE, Vienna, VA  22180).


7. Editors' Addresses

Ray Denenberg
Library of Congress
Collections Services
Network Development/MSO
Washington DC 20540
ray@rden.loc.gov
Voice: (202) 707-5795
Fax:   (202) 707-0115

John A. Kunze
Center for Knowledge Management
University of California, San Francisco
530 Parnassus Ave, Box 0840
San Francisco, CA  94143-0840
jak@ckm.ucsf.edu
Voice: (415) 502-6660
Fax:   (415) 476-4653

Denis Lynch
TRW Business Intelligence Systems
1329 Moffet Park Drive
Sunnyvale, CA 94089
dml@bis.trw.com
Voice: (408) 541-6418
Fax:   (408) 541-6401
1
2	IETF URI Working Group R. Denenberg
3	Internet-Draft J. Kunze
4	draft-ietf-uri-url-irp-04.txt D. Lynch
5	5 February 1996 Editors
6	Expires in six months
7
8	Uniform Resource Locators for Z39.50
9
10
11	1. Status of this Document
12
13	This document is an Internet-Draft. Internet-Drafts are working documents
14	of the Internet Engineering Task Force (IETF), its Areas, and its Working
15	Groups. Note that other groups may also distribute working documents as
16	Internet-Drafts.
17
18	Internet-Drafts are working documents valid for a maximum of six months.
19	Internet-Drafts may be updated, replaced, or obsoleted by other documents
20	at any time. It is not appropriate to use Internet-Drafts as reference
21	material or to cite them other than as a ``working draft' or ``work in
22	progress.''
23
24	To learn the current status of any Internet-Draft, please check the
25	1id-abstracts.txt listing contained in the Internet-Drafts Shadow
26	Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
27	munnari.oz.au.
28
29	Distribution of this document is unlimited. Please send comments to
30	jak@violet.berkeley.edu, or to the discussion lists uri@bunyip.com and
31	z3950iw@nervm.nerdc.ufl.edu.
32
33
34	2. Introduction
35
36	Z39.50 is an information retrieval protocol that does not fit neatly into
37	a retrieval model designed primarily around the stateless fetch of data.
38	Instead, it models a general user inquiry as a session-oriented, multi-
39	step task, any step of which may be suspended temporarily while the
40	server requests additional parameters from the client before continuing.
41	Some, none, or all of these client/server interactions may require
42	participation of the client user, depending only on the client software
43	(the protocol itself makes no such requirements).
44
45	On the other hand, retrieval of "well-known" data may be performed in
46	a single step, that is, with a degenerate Z39.50 session consisting of
47	exactly one protocol search request and response. Besides the basic
48	search sub-service, there are several ancillary sub-services (e.g., Scan,
49	Result Set Delete). Among the functions covered by combinations of the
50	sub-services, two core functions emerge as appropriately handled by two
51	separate URL schemes: the Session URL and the Retrieval URL.
52
53	Using two schemes instead of one makes a critical distinction between a
54	Z39.50 Session URL, which opens a client session initialized for
55	interactive use by the user, and a Z39.50 Retrieval URL, which opens and
56	closes a client session to retrieve a specific information item. Making
57	this distinction at the scheme level allows the user interface to reflect
58	it on to the user, without requiring the user interface to parse otherwise
59	opaque parts of the URL (consistent with current practice).
60
61
62	3. The Z39.50 Session URL
63
64	The Z39.50 Session URL may be informally described as providing the
65	mechanism to switch the user to a Z39.50 client application.
66
67	- Host is required.
68	- Port is optional, and defaults to 210.
69	- All other parameters are optional.
70	- The Z39.50 client will start a session to the specified host/port
71	(alternatively, it need not explicitly start a session, but may
72	instead utilize an already open session to the same host/port).
73	- A database must be included if docid is included.
74	- If docid is included, the client will perform the specified search
75	(in the same manner as for the retrieval URL, specified below).
76	- If docid is not included, and other parameters (besides host/port)
77	are specified, the client may use those parameters as "hints".
78	Various clients may choose to treat them as requirements, or as
79	preferences, or ignore them.
80	- In any case (whether a search is performed or not), the client will
81	leave the Z39.50 session open for the user, to do retrievals, new
82	searches, etc. (This is the main distinction from the Retrieval URL
83	which leaves it up to the client whether or not to keep the Z39.50
84	session open.)
85
86
87	4. The Z39.50 Retrieval URL
88
89	The Z39.50 Retrieval URL is intended to allow a Z39.50 session to be used as
90	a transparent transfer mechanism to retrieve a specific information object.
91	A Z39.50 client uses information in the URL to formulate a Search Request.
92	The server's Search Response indicates how many records match the Request.
93	If the number of matching records does not equal one, the retrieval is
94	considered unsuccessful, and the client application's behavior is not defined.
95	If the number of matching records equals one, the server may have included
96	the desired record in the Search Response. If not, the client requests
97	transmission of the record with a Present Request. After the client has
98	received the specified record it may close the Z39.50 session immediately,
99	or keep it open for subsequent retrievals.
100
101	- Host is required.
102	- Port is optional, and defaults to 210.
103	- A database is required.
104	- The meaning of a retrieval URL with no docid is undefined.
105	- The docid is placed into a type-1 query, as the single term, in
106	the general format (tag 45), using the Bib-1 attribute set, with
107	a Use attribute value of docid, and a structure attribute of URx.
108	The docid string is server-defined and completely opaque to the client.
109	- If element set name (esn) is not specified, it is the client's choice.
110	If esn is specified, it should be used either in the Search
111	request for the value of small- and/or medium- set-element-set-names
112	or in a Present request following a Search. These terms and their
113	use are defined within the Z39.50 Standard [2].
114	- If record syntax (rs) is not specified, it is the client's choice.
115	If one or more record syntaxes are specified, the client should select
116	one (preferably the first in the list that it supports) and use it in
117	a Search or Present request as the value of PreferredRecordSyntax.
118
119
120	5. BNF for Z39.50 URLs
121
122	The Z39.50 Session and Retrieval URLs follow the Common Internet Scheme
123	Syntax as defined in RFC 1738, "Uniform Resource Locators (URL)" [1].
124	In the definition, literals are quoted with "", optional elements
125	are enclosed in [brackets], "\|" is used to designate alternatives,
126	and elements may be preceded with <n>* to designate n or more
127	repetitions of the following element; n defaults to 0.
128
129	z39.50url = zscheme "://" host [":" port]
130	["/" [database *["+" database]
131	["?" docid]]
132	[";esn=" elementset]
133	[";rs=" recordsyntax *[ "+" recordsyntax]]]
134
135	zscheme = "z39.50r" \| "z39.50s"
136	database = uchar
137	docid = uchar
138	elementset = uchar
139	recordsyntax = uchar
140
141	Future extensions to these URLs will be of the form of [;keyword=value].
142
143	The following definitions are from RFC 1738. Between the Internet Draft
144	version and RFC 1738 two relevant changes were made: '=' was moved from
145	the <extra> character class to <reserved>, and <national> was removed from
146	the alternatives in <unreserved>. Neither <national> nor <punctuation> is
147	referred to in this document nor in RFC 1738.
148
149	lowalpha = "a" \| "b" \| "c" \| "d" \| "e" \| "f" \| "g" \| "h" \|
150	"i" \| "j" \| "k" \| "l" \| "m" \| "n" \| "o" \| "p" \|
151	"q" \| "r" \| "s" \| "t" \| "u" \| "v" \| "w" \| "x" \|
152	"y" \| "z"
153	hialpha = "A" \| "B" \| "C" \| "D" \| "E" \| "F" \| "G" \| "H" \| "I" \|
154	"J" \| "K" \| "L" \| "M" \| "N" \| "O" \| "P" \| "Q" \| "R" \|
155	"S" \| "T" \| "U" \| "V" \| "W" \| "X" \| "Y" \| "Z"
156
157	alpha = lowalpha \| hialpha
158	digit = "0" \| "1" \| "2" \| "3" \| "4" \| "5" \| "6" \| "7" \|
159	"8" \| "9"
160	safe = "$" \| "-" \| "_" \| "." \| "+"
161	extra = "!" \| "*" \| "'" \| "(" \| ")" \| ","
162	national = "{" \| "}" \| "\|" \| "\" \| "^" \| "~" \| "[" \| "]" \| "`"
163	punctuation = "<" \| ">" \| "#" \| "%" \| <">
164
165	reserved = ";" \| "/" \| "?" \| ":" \| "@" \| "&" \| "="
166	hex = digit \| "A" \| "B" \| "C" \| "D" \| "E" \| "F" \|
167	"a" \| "b" \| "c" \| "d" \| "e" \| "f"
168	escape = "%" hex hex
169	unreserved = alpha \| digit \| safe \| extra
170	uchar = unreserved \| escape
171	xchar = unreserved \| reserved \| escape
172	digits = 1*digit
173
174	6. Security Considerations
175
176	The two Z39.50 URL schemes are subject to the same security implications
177	as the general URL scheme [1], so the usual precautions apply. This means,
178	for example, that a locator might no longer point to the object that was
179	originally intended. It also means that it may be possible to construct
180	a URL so that an attempt to perform a harmless idempotent operation such
181	as the retrieval of an object will in fact cause a possibly damaging
182	remote operation to occur.
183
184
185	7. Acknowledgements
186
187	The Z39.50 Implementors Group contributed the substance of this document.
188
189
190	8. References
191
192	[1] Berners-Lee, T., Masinter, L., McCahill, M. (editors), "Uniform
193	Resource Locators (URL)", RFC 1738, December 1994.
194	ftp://ds.internic.net/rfc/rfc1738.txt
195
196	[2] ANSI/NISO Z39.50-1994, "ANSI Z39.50: Information Retrieval Service
197	and Protocol", 1994. ftp://ftp.loc.gov/pub/z3950/
198
199	[3] ANSI/NISO Z39.50-1992, "ANSI Z39.50: Information Retrieval Service
200	and Protocol", 1992.
201	ftp://ftp.cni.org/pub/NISO/docs/Z39.50-1992/www/Z39.50.toc.html
202	(also available in hard copy from Omnicom Information Service,
203	115 Park St., SE, Vienna, VA 22180).
204
205
206	7. Editors' Addresses
207
208	Ray Denenberg
209	Library of Congress
210	Collections Services
211	Network Development/MSO
212	Washington DC 20540
213	ray@rden.loc.gov
214	Voice: (202) 707-5795
215	Fax: (202) 707-0115
216
217	John A. Kunze
218	Center for Knowledge Management
219	University of California, San Francisco
220	530 Parnassus Ave, Box 0840
221	San Francisco, CA 94143-0840
222	jak@ckm.ucsf.edu
223	Voice: (415) 502-6660
224	Fax: (415) 476-4653
225
226	Denis Lynch
227	TRW Business Intelligence Systems
228	1329 Moffet Park Drive
229	Sunnyvale, CA 94089
230	dml@bis.trw.com
231	Voice: (408) 541-6418
232	Fax: (408) 541-6401