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1 INTERNET-DRAFT J. Salsman
2 Suggested filename: <draft-www-device-upload-00.txt> WebTV Networks
3 Expiration date: 15 May 1998 12 November 1997
4
5 Form-based Device Input and Upload in HTML
6
7 Status of this Memo
8
9 This draft extends an experimental protocol for the Internet
10 community. This draft does not specify an Internet standard of any
11 kind. Discussion and suggestions for improvement are requested.
12 Distribution of this memo will be unlimited when the W3C approves the
13 HTML 4.0 standard. Until then, please do not distribute this draft
14 beyond your department.
15
16 1. Abstract and introduction
17
18 Currently, HTML forms allow the producer of the form to request
19 information -- including files of data -- from the operator reading
20 the form. However, this capability is limited because HTML forms
21 don't provide a way to ask the operator to submit input from
22 arbitrary sources such as audio devices like microphones. Since
23 input and upload from various devices is a feature that will
24 benefit many applications, this draft proposes an extension to the
25 HTML INPUT TYPE=FILE form element specified in RFC 1867 to allow
26 information providers to express requests for uploads from audio
27 and other devices uniformly, and a discussion of MIME audio data
28 types to facilitate useful audio upload responses. This draft also
29 includes security and audio usability and quality discussions as
30 well as a description of a backward compatibility strategy that
31 allows new user agents to utilize HTML written with earlier
32 proposals for audio input in mind, and concludes with motivations.
33
34 This document is an Internet-Draft. Internet-Drafts are working
35 documents of the Internet Engineering Task Force (IETF), its
36 areas, and its working groups. Note that other groups may also
37 distribute working documents as Internet-Drafts.
38
39 Internet-Drafts are draft documents valid for a maximum of six
40 months and may be updated, replaced, or obsoleted by other
41 documents at any time. It is inappropriate to use Internet-
42 Drafts as reference material or to cite them other than as
43 "work in progress."
44
45 To view the entire list of current Internet-Drafts, please check
46 the "1id-abstracts.txt" listing contained in the Internet-Drafts
47 Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net
48 (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
49 Coast), or ftp.isi.edu (US West Coast).
50
51 2. HTML forms with device input file upload submission
52
53 Section 3.1 of RFC 1867 provides for the presentation of an
54 arbitrary "widget" to specify input for file uploads. When an
55 INPUT tag of type FILE is encountered with a DEVICE attribute, the
56 associated value (such as MICROPHONE, or MIC) might select the use
57 of a widget capable of buffering and editing real-time input (such
58 as speech) instead of entering a file selection mode.
59
60 If an ACCEPT attribute is present in a device file input element,
61 the browser might constrain the MIME type of uploaded data to match
62 those with the corresponding list of types specified. If the value
63 of the DEVICE parameter is FILESYSTEM or FILES then the INPUT
64 element might be treated as usual according to RFC 1867 except that
65 the subset of files presented to the operator to choose from may be
66 constrained by the specified list of MIME types instead of a
67 pattern of file names or extensions.
68
69 Since there is no original filename as specified in section 3.3 of
70 RFC 1867 for parameters of the 'content-disposition: form-data' and
71 'content-disposition: file' HTTP headers, those headers might be
72 provided with a 'type' parameter representing the MIME type of the
73 encoded data, if known, and a 'device' parameter with the same
74 value as the DEVICE attribute of the associated form input element,
75 unless the device or MIME type(s) specified are unsupported in
76 which case the value of the 'device' header parameter might be
77 'unsupported', or unless the device is unavailable in which case
78 the value might be 'unavailable'. If the MIME types requested are
79 unsupported, an additional parameter 'alternates' might be included
80 with a space-separated list of MIME types of the same content-type
81 which may be supported as alternatives for the specified device.
82
83 There may be significant limitations on the client browser's
84 ability to buffer input for upload. Browsers might provide an
85 estimate of the default MAXLENGTH available for device input and
86 upload through the HTTP header 'Pragma: DEVICE-MAXLENGTH='BYTES
87 which represents the content-length available to the browser for
88 buffering (see section 14.32 of RFC 2068.)
89
90 Furthermore, the VALUE attribute may be used to provide a
91 disambiguation between multiple similar devices when present.
92
93 If real time events, such as those described and proposed by
94 Gregory S. Aist in "A General Architecture for a Real-Time
95 Discourse Agent and a Case Study in Computerized Oral Reading
96 Tutoring" (Carnegie Mellon University Computational Linguistics
97 Program, 6 December 1996), are required, then the Real-time
98 Transport Protocol (RTP, currently RFC 1889) should be used
99 instead. Because of security concerns discussed in section 3
100 below, HTML scripts might not be able to invoke a form submission
101 when the form involves any kind of file upload without explicit
102 instructions from the session operator to the contrary.
103
104 2.1. Examples
105
106 <FORM ENCTYPE="multipart/form-data" METHOD=POST ACTION="_URL_">
107 Say something: <INPUT NAME=SPEECH1 TYPE=FILE DEVICE=MIC>
108 <INPUT TYPE=SUBMIT VALUE="Send Speech">
109 </FORM>
110
111 In this simple form, the HTML author has requested the upload of
112 sampled microphone input from the operator upon form submission.
113
114 <INPUT NAME=SPEECH2 TYPE=FILE DEVICE=MICROPHONE
115 ACCEPT="audio/l16 ;rate=11025 ;channels=1 audio/x-cepstral-voc">
116
117 Here MIC is not used as an abbreviation. The author of the HTML has
118 requested that the data input from the microphone be encoded as
119 either
120 the MIME type Audio/L16 -- sixteen bit signed linear audio samples
121 (most-significant byte first) -- as specified in RFC 1890 section
122 4.4.8, with a single (monaural) channel and a sample rate of 11,025
123 samples per second, or an unspecified extended MIME Audio type named
124 'x-cepstral-voc'.
125
126 <INPUT NAME=FILE1 TYPE=FILE DEVICE=FILES ACCEPT="text/*">
127
128 Here the form element may be used to upload a file as usual, except
129 that the files to select from might be constrained to text files,
130 without explicit regard of their filename or extensions.
131
132 <INPUT NAME=PICTURE1 TYPE=FILE DEVICE=CAMERA VALUE=2>
133
134 The final example shows how these extensions may be used to request
135 input from other kinds of devices, such as the second of two or
136 more cameras connected to the system running the browser.
137
138 3. Security considerations
139
140 Browser operators may not want to send their files, recordings,
141 pictures, video, or other device inputs to arbitrary sites without
142 their explicit permission and direction. Therefore, browser
143 authors are encouraged to disallow the submission of forms which
144 include any kind of file upload by any means other than the
145 standard HTML operator-controlled buttons for form submission
146 without explicit instruction from the session operator to the
147 contrary. Accordingly, the SIZE parameter, document style sheets,
148 and document layers may be prevented from obscuring any kind of
149 file upload widget, especially those capable of accepting a default
150 filename. Finally, just as the operator may take direct action to
151 initiate, terminate, review and edit recording as described in the
152 next section, browser authors are encouraged to prevent HTML
153 scripts from taking those and similar actions, unless for example
154 the operator has specifically enabled such script actions with a
155 security option. Even then, such preferences might be specified by
156 the operator to reset after an interval or at the end of the
157 session. Furthermore, explicit information might be provided to
158 insure that the operator is informed when files are being uploaded.
159
160 4. User interface usability and quality concerns for audio
161
162 An audio sample is customarily recorded on computer equipment with
163 a dialog routine capable of allowing the user to record, pause,
164 play back, erase, or otherwise edit the recording. Browsers might
165 provide the operator with the same kind of dialog routine for audio
166 device input. And if a MAXLENGTH has been specified or is in force
167 because of limited buffer size, a display of the buffer size used
168 and remaining might be displayed as a dynamic bar graph (or
169 percentage if graphics are unavailable.) A display of time in
170 seconds used and remaining in the buffer may also be provided.
171
172 Most MIME types defined for audio do not provide high-quality audio
173 encodings. The 'audio/basic' and other types which use a sample
174 rate of 8,000 samples per second truncate the audio spectrum at
175 4,000 Hz according to the Nyquist theorem, discarding information
176 important for discerning consonants. Also, audio/basic and other
177 MIME Audio types use a sample size of eight bits, which does not
178 usually provide enough dynamic range for accurate automatic speech
179 recognition unless published automatic gain control algorithms are
180 reliably used. If sixteen-bit unsigned audio encodings are used
181 according to section 4.4.8 of RFC 1890, the sample rate --
182 specified as the 'rate' parameter of the MIME type 'audio/l16' --
183 might be at least 11,025 or 16,000 to adequately provide sufficient
184 information for automatic speech recognition. Otherwise, the audio
185 feature extraction encoding of the speech recognition algorithm
186 might be used to provide a more compact representation to shorten
187 the upload.
188
189 5. Compatibility with earlier forms of audio input
190
191 Audio device input has been proposed before and implemented from a
192 microphone at least as early as 1994 in experimental versions of
193 common Web browsers. To accommodate the syntax of these earlier
194 extensions, a browser might interpret a valid XML statement such as
195
196 <INPUT TYPE=AUDIO ...>
197
198 as the device input form
199
200 <INPUT TYPE=FILE DEVICE=MICROPHONE ...>
201
202 with all other attribute/value pairs of the original INPUT element
203 kept the same as specified. This would retain compatibility for
204 all implementations of which the author of this draft is aware.
205
206 6. HTML Document Type Description changes
207
208 Along with the extension to the HTML InputType entity described in
209 the previous section, this proposal makes an addition to the HTML
210 DTD for the INPUT element ATTLIST of an #IMPLIED attribute DEVICE
211 of type CDATA.
212
213 7. Motivations and conclusion
214
215 The primary motivation for these extensions is to add the
216 capability of speech input to Web-based educational systems. For
217 example, the "Test of English as a Foreign Language," or TOEFL
218 assessment is comprised of multiple choice questions based on media
219 comprised of text and audio recordings, so it would be possible to
220 represent the TOEFL with current HTML multimedia content and forms.
221 However, the TOEFL makes no provision whatsoever about the accuracy
222 of pronunciation by the subjects of the assessment, except that
223 provided by the ability to accurately identify the terms in the
224 text of the assessment. So while scoring on the important ability
225 to listen, the TOEFL does not make provisions to assess the
226 important ability to speak with correct pronunciation. But with
227 form-based audio input and upload, and speech recognition servers
228 capable of aligning and scoring the pronunciation of words and
229 phonemes, such a Web-based TOEFL could be extended to reduce the
230 number of inscrutable graduate teaching assistants, for example.
231 Of course the possibilities for language instruction enabled by
232 these extensions are not limited to the graduate level or English.
233
234 Other motivations include the development of "dictation servers"
235 capable of transforming spoken audio uploaded though an HTTP
236 session to the corresponding text suitable for sending in email or
237 including in another document, for example. Natural language
238 continuous speech recognition software conforming to standard APIs
239 for automatic dictation is as of this writing available from retail
240 outlets for less than US$90 so there is ample reason to believe
241 that dictation servers could soon become commonplace on the Web
242 with these extensions.
243
244 Finally, this could be a great help for hearing impaired people who
245 want to use a "phonology server" (similar to the server described
246 in the Web-TOEFL example above) to practice improving their
247 pronunciation without depending on a human speech coach.
248
249 The change to the HTML DTD is very simple, but very powerful. It
250 enables a much greater variety of services to be implemented via
251 the World-Wide Web than is currently possible due to the lack of a
252 peripheral input upload submission facility. This would be a very
253 valuable addition to the capabilities of the World-Wide Web.
254
255 8. Author's address and acknowledgments
256
257 James Salsman
258 Bovik Research (nonprofit research institute)
259 courtesy WebTV Networks, Microsoft Corporation
260 and MindSource Software Engineers
261
262 575 S. Rengstorff Avenue
263 Mountain View, CA 94040-1982
264
265 Email: jps@bovik.org, jsalsman@corp.webtv.net
266 Phone: (650) 938-1440
267
268 "TOEFL" and "Test Of English as a Foreign Language" are
269 registered trademarks of Educational Testing Service.
270
271 References
272
273 [RFC 1867] Form-based File Upload in HTML. E. Nebel & L. Masinter,
274 November 1995. ftp://ds.internic.net/rfc/rfc1867.txt
275
276 [RFC 1889] RTP: A Transport Protocol for Real-Time Applications.
277 H. Schulzrinne, S. Casner, R. Frederick, & V. Jacobson,
278 January 1996. ftp://ds.internic.net/rfc/rfc1889.txt
279
280 [RFC 1890] RTP Profile for Audio and Video Conferences with Minimal
281 Control. H. Schulzrinne, January 1996.
282 ftp://ds.internic.net/rfc/rfc1890.txt
283
284 [RFC 2068] Hypertext Transfer Protocol -- HTTP/1.1. R. Fielding,
285 J. Gettys, J. Mogul, H. Frystyk, & T. Berners-Lee,
286 January 1997. ftp://ds.internic.net/rfc/rfc2068.txt
287

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