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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (September 7, 1998) is 9356 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'SI' Summary: 9 errors (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT Larry Masinter 2 draft-ietf-conneg-media-features-02.txt Koen Holtman 3 Andy Mutz 4 Dan Wing 5 expires in 6 months September 7, 1998 7 Media Features for Display, Print, and Fax 9 Status of this memo 11 This document is an Internet-Draft. Internet-Drafts are working 12 documents of the Internet Engineering Task Force (IETF), its areas, 13 and its working groups. Note that other groups may also distribute 14 working documents as Internet-Drafts. 16 Internet-Drafts are draft documents valid for a maximum of six 17 months and may be updated, replaced, or obsoleted by other 18 documents at any time. It is inappropriate to use Internet-Drafts 19 as reference material or to cite them other than as "work in 20 progress." 22 To view the entire list of current Internet-Drafts, please check 23 the "1id-abstracts.txt" listing contained in the Internet-Drafts 24 Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net 25 (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au 26 (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu 27 (US West Coast). 29 Copyright (C) The Internet Society (1997). All Rights Reserved. 31 Abstract 33 This specification defines some common media features for 34 describing image resolution, size, color, and image representation 35 methods that are common to web browsing, printing, and facsimile 36 applications. These features are registered for use within the 37 framework of [REG]. 39 1. Introduction 41 This work was originally motivated by the requirements from web 42 browsers to send the browser's display characteristics to the web 43 server to allow the server to choose an appropriate representation. 45 This specification defines some common media features [REG] by 46 which a recipient may inform a sender as to the characteristics of 47 its message handling. The sender may then provide the variant of 48 the message that is most suitable for the recipient. 50 Different variants would typically be higher or lower resolution 51 images (for example) as appropriate. In the case of a sending to a 52 printer, the result would be higher quality output. In the case of 53 a small screen device (cellphone, portable digital assistant), the 54 result would be faster transmission. 56 Media features may be used in many different protocol situations. 57 Those defined in this specification can indicate the display or 58 printer dimensions (in pixels), color capability and bit-depth, or 59 media type. The physical dimensions of a display can be inferred 60 from the display size and display resolution. In the case of paper 61 output, the paper size may be expressed as a token from a list of 62 standard paper sizes. These are presented formally in the 63 Notation section. 65 2. Media Feature Registrations 67 This section defines several media features, using the form 68 specified in [REG]. 70 2.1 Image Size 72 - Media Feature tag name(s): 74 pix-x 75 pix-y 77 - ASN.1 identifier associated with this feature tag: 79 ***New assignments by IANA*** 81 - Summary of the media features indicated by this feature tag: 83 These features indicate the display size of the recipient for 84 display or print, measured in pixels; they indicate horizontal 85 (pix-x) and vertical (pix-y) dimensions. 87 - Values appropriate for use with this feature tag: 89 Signed Integer 91 - The feature tag is intended primarily for use in the following 92 applications, protocols, services, or negotiation mechanisms: 94 Display and print applications where different media choices will 95 be made depending on the size of the recipient device. For 96 example, a web application for use on a 240x480 display might use 97 different HTML pages than one intended for use on a 1024x768 98 display. 100 2.2 Resolution 102 - Media Feature tag name: 104 dpi 106 - ASN.1 identifier associated with this feature tag: 108 ***New assignments by IANA*** 110 - Summary of the media features indicated by this feature tag: 112 This feature indicates the resolution that the recipient can 113 display or print without loss, measured in pixels per inch. 114 Typically resolution capability is represented as dots-per-inch 115 rather than in SI units [SI]. Values for dpi may be expressed as 116 a rational to accomodate resolution of SI-based devices; for 117 example dpi=19558/100 can be used to represent a resolution of 77 118 dots per centimeter. 120 - Values appropriate for use with this feature tag: 122 Rational 124 - The feature tag is intended primarily for use in the following 125 applications, protocols, services, or negotiation mechanisms: 127 Printing and fax applications typically choose representations 128 of a transmitted document depending on the resolution of 129 the recipient rather than pixel size. 131 - Examples of typical use: 133 Choosing a version of a printable document to send to 134 a printer. 136 - Considerations particular to use in individual applications, 137 protocols, services, or negotiation mechanisms: 139 Software applications are typically unaware of the resolution of 140 the display. 142 2.3 Registration of 'media' 143 - Media Feature tag name(s): 145 ua-media 147 - ASN.1 identifier associated with this feature tag: 149 ***New assignments by IANA*** 151 - Summary of the media features indicated by this feature tag: 153 This feature indicates the recipients device media, indicated 154 with an simple token. 156 - Values appropriate for use with this feature tag: 158 Token with an equality relationship. Typical values include: 160 screen A refreshable display 161 screen-paged a refreshable display which cannot scroll 162 stationery Separately cut sheets of an opaque material 163 transparency Separately cut sheets of a transparent material 164 envelope Envelopes that can be used for conventional 165 mailing purposes 166 envelope-plain Envelopes that are not preprinted and have no 167 windows 168 continuous Continuously connected sheets of an opaque 169 material 171 - The feature tag is intended primarily for use in the following 172 applications, protocols, services, or negotiation mechanisms: 174 Most of the feature values are useful for printing applications, 175 or to distinguish printing from display. 177 - Examples of typical use: 179 This might typically be used for selecting between a rendition 180 that is intended to be printed and one that is intended to 181 be displayed. 183 - Considerations particular to use in individual applications, 184 protocols, services, or negotiation mechanisms: 186 Other media values were not included because their utility 187 seemed relative. 189 - Interoperability considerations: 191 Interoperability with the Internet Print Protocol means that 192 some additional feature values may need to be registered. 194 2.4 Paper Size 196 - Media Feature tag name(s): 198 paper-size 200 - ASN.1 identifier associated with this feature tag: 202 ***New assignment by IANA*** 204 - Summary of the media features indicated by this feature tag: 206 For stationery, it is often useful to have information about the 207 size of display used. While it is more precise and predictable 208 to use absolute resolution and pixel sizes, some applications 209 find it useful to provide paper size in addition to this 210 information. Note that not all of the paper may have a printable 211 area. 213 - Values appropriate for use with this feature tag: 214 String with equality 216 letter: 8.5x11.0 inches 217 A4: 210x297 mm 218 B4: 250x353 mm 219 A3: 297x420 mm 220 legal: 8.5x14 inches 222 - The feature tag is intended primarily for use in the following 223 applications, protocols, services, or negotiation mechanisms: 225 This feature tag seems most useful for the printing application. 227 - Examples of typical use: 229 Choosing between a4 and letter size renditions of the 230 same printable document. 232 2.5 Color and greyscale 233 - Media Feature tag name(s): 235 color 236 grey 238 - ASN.1 identifier associated with this feature tag: 240 ***New assignments by IANA*** 242 - Summary of the media features indicated by this feature tag: 244 The color capabilities of the recipient are indicated with 245 feature value describing the number of color (or greyscale) 246 channel bits available. 248 - Values appropriate for use with this feature tag: 250 Integer 252 Values are typically (but not limited to) 2, 8, or 24. For 253 example: grey=8 indicates a display capable of representing an 254 image in 256 levels of a single color, while color=8 indicates a 255 display capable of representing an image with a palette of 256 256 colors. 258 - The feature tag is intended primarily for use in the following 259 applications, protocols, services, or negotiation mechanisms: 261 Web applications may choose between color, greyscale, or binary 262 representations. Fax applications may choose between color 263 and non-color renditions. 265 - Examples of typical use: 267 n/a 269 - Related standards or documents: 271 n/a 273 - Considerations particular to use in individual applications, 274 protocols, services, or negotiation mechanisms: 276 n/a 278 - Interoperability considerations: 280 n/a 282 - Security considerations: 284 n/a 286 - Privacy concerns, related to exposure of personal information: 288 n/a 290 - Denial of service concerns related to consequences of specifying 291 incorrect values: 293 n/a 295 - Additional information: 297 n/a 299 - Keywords: 301 n/a 302 - Related feature tags: 304 - Related media types or data formats: 306 - Related markup tags: 308 - Name(s) & email address(es) of person(s) to contact for 309 further information: 311 - Intended usage: 312 COMMON 314 - Author/Change controller: 316 3. Examples of use of features 318 The following examples of feature comparison show how these features 319 can be used to describe various capabilities. The syntax used to 320 express combinations of features is purely illustrative and not 321 normative: 323 pix-x<=1024, pix-y<=768 324 indicates a 1024x768 display 326 dpi<=72 327 indicates a 72 dpi display 329 ua-media=stationery 330 indicates the display is a cut sheet of opaque material, such as 331 paper. 333 paper-size=iso-a4 334 indicates the display size is 210x297mm. 336 color<=24 337 indicates the display supports 24-bit (8-bit/channel) color. 339 4. IANA considerations 341 This document calls for registration of the following feature tags, 342 as per [REG]: pix-x, pix-y, dpi, ua-media, paper-size, color, grey, 343 ASN.1 identifiers should be assigned to each of these and replaced 344 in the body of the registration. 346 4. Acknowledgments 348 This document is based on a previous draft co-authored with Lou 349 Montoulli. It had benefited from the comments of Graham Klyne, Ho 350 John Lee, Brian Behlendorf, Jeff Mogul, and Ted Hardie. 352 References 354 [REG] A. Mutz, T. Hardie. "Feature Tag Registration Procedures", 355 draft-ietf-conneg-feature-reg-03.txt, July 1998. 357 [SI] ISO 1000:1992 "SI units and recommendations for the use of 358 their multiples and of certain other units", International 359 Organization for Standardization, 1992. 361 Author's Addresses 363 Larry Masinter 364 Xerox Palo Alto Research Center 365 3333 Coyote Hill Road 366 Palo Alto CA 94304 367 Fax +1 415 812 4333 368 Email: masinter@parc.xerox.com 370 Dan Wing 371 Cisco Systems, Inc. 372 101 Cooper Street 373 Santa Cruz, CA 95060 USA 374 Phone: +1 408 457 5200 375 Fax: +1 408 457 5208 376 EMail: dwing@cisco.com 378 Andrew H. Mutz 379 Hewlett-Packard Company 380 1501 Page Mill Road 3U-3 381 Palo Alto CA 94304, USA 382 Fax +1 415 857 4691 383 Email: mutz@hpl.hp.com 385 Koen Holtman 386 Technische Universiteit Eindhoven 387 Postbus 513 388 Kamer HG 6.57 389 5600 MB Eindhoven (The Netherlands) 390 Email: koen@win.tue.nl