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Network Working Group                                      L. MasinterRequest for Comments: 2534                           Xerox CorporationCategory: Standards Track                                      D. Wing                                                   Cisco Systems, Inc.                                                               A. Mutz                                                 Jutvision Corporation                                                            K. Holtman                                                                   TUE                                                            March 1999Media Features for Display, Print, and FaxStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   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 (1999).  All Rights Reserved.Abstract   This specification defines some common media features for describing   image resolution, size, color, and image representation methods that   are common to web browsing, printing, and facsimile applications.   These features are registered for use within the framework of [REG].1. Introduction   This work was originally motivated by the requirements from web   browsers to send the browser's display characteristics to the web   server to allow the server to choose an appropriate representation.   This specification defines some common media features [REG] by which   a recipient may inform a sender as to the characteristics of its   message handling.  The sender may then provide the variant of the   message that is most suitable for the recipient.   Different variants would typically be higher or lower resolution   images (for example) as appropriate.  In the case of a sending to a   printer, the result would be higher quality output.  In the case of a   small screen device (cellphone, portable digital assistant), the   result would be faster transmission.Masinter, et al.            Standards Track                     [Page 1]

RFC 2534       Media Features for Display, Print, and Fax     March 1999   Media features may be used in many different protocol situations.   Those defined in this specification can indicate the display or   printer dimensions, resolution, color capability.  The physical   dimensions of a display may be inferred from the display size and   display resolution. In the case of paper output, the paper size may   be expressed as a token from a list of standard paper sizes.  These   are presented formally in the Notation section.2. Media Feature Registrations   This section defines several media features, using the form specified   in [REG].2.1 Image Size   - Media Feature tag name(s):     pix-x     pix-y   - ASN.1 identifier associated with this feature tag:     1.3.6.1.8.1.1     1.3.6.1.8.1.2   - Summary of the media features indicated by this feature tag:     These features indicate the display size of the recipient for     display or print, measured in pixels; they indicate horizontal     (pix-x) and vertical (pix-y) dimensions.   - Values appropriate for use with this feature tag:     Signed Integer   - The feature tag is intended primarily for use in the following     applications, protocols, services, or negotiation mechanisms:     Display and print applications where different media choices will     be made depending on the size of the recipient device. For     example, a web application for use on a 240x480 display might use     different HTML pages than one intended for use on a 1024x768     display.Masinter, et al.            Standards Track                     [Page 2]

RFC 2534       Media Features for Display, Print, and Fax     March 19992.2 Resolution   - Media Feature tag name:     dpi   - ASN.1 identifier associated with this feature tag:     1.3.6.1.8.1.3   - Summary of the media features indicated by this feature tag:     This feature indicates the resolution that the recipient can     display or print without loss, measured in pixels per inch.     Typically resolution capability is represented as dots-per-inch     rather than in SI units [SI]. Values for dpi may be expressed as a     rational to accomodate resolution of SI-based devices; for example     dpi=19558/100 can be used to represent a resolution of 77 dots per     centimeter.   - Values appropriate for use with this feature tag:     Rational   - The feature tag is intended primarily for use in the following     applications, protocols, services, or negotiation mechanisms:     Printing and fax applications typically choose representations of     a transmitted document depending on the resolution of the     recipient rather than pixel size.   - Examples of typical use:     Choosing a version of a printable document to send to a printer.   - Considerations particular to use in individual applications,     protocols, services, or negotiation mechanisms:     Software applications are typically unaware of the resolution of     the display. Note that there exist devices with different     resolution in different directions, i.e., individual pixels are     not square. However, this feature only encompasses the     uniform resolution.Masinter, et al.            Standards Track                     [Page 3]

RFC 2534       Media Features for Display, Print, and Fax     March 19992.3 Registration of 'ua-media'   - Media Feature tag name(s):     ua-media   - ASN.1 identifier associated with this feature tag:     1.3.6.1.8.1.4     - Summary of the media features indicated by this feature tag:     This feature indicates the recipients device media, indicated with     an simple token.   - Values appropriate for use with this feature tag:     Token with an equality relationship. Values include:     screen           A refreshable display     screen-paged     a refreshable display which cannot scroll     stationery       Separately cut sheets of an opaque material     transparency     Separately cut sheets of a transparent material     envelope         Envelopes that can be used for conventional                      mailing purposes     envelope-plain   Envelopes that are not preprinted and have no                      windows     continuous       Continuously connected sheets of an opaque                      material   - The feature tag is intended primarily for use in the following     applications, protocols, services, or negotiation mechanisms:     Most of the feature values are useful for printing applications, or     to distinguish printing from display.   - Examples of typical use:     This might typically be used for selecting between a rendition that     is intended to be printed and one that is intended to be displayed.   - Considerations particular to use in individual applications,     protocols, services, or negotiation mechanisms:     Other media values were not included because their utility seemed     relative.Masinter, et al.            Standards Track                     [Page 4]

RFC 2534       Media Features for Display, Print, and Fax     March 1999   - Interoperability considerations:     Interoperability with the Internet Print Protocol means that some     additional feature values may need to be registered.2.4 Paper Size   - Media Feature tag name(s):     paper-size   - ASN.1 identifier associated with this feature tag:     1.3.6.1.8.1.5   - Summary of the media features indicated by this feature tag:     For stationery, it is often useful to have information about the     size of display used.  While it is more precise and predictable to     use absolute resolution and pixel sizes, some applications find it     useful to provide paper size in addition to this information. Note     that not all of the paper may have a printable area.   - Values appropriate for use with this feature tag:     Token with an equality relationship. Typical values include:      letter        8.5x11.0 inches      a4            210x297 mm      b4            250x353 mm      a3            297x420 mm      legal         8.5x14 inches   - The feature tag is intended primarily for use in the following     applications, protocols, services, or negotiation mechanisms:     This feature tag seems most useful for the printing application.   - Examples of typical use:     Choosing between a4 and letter size renditions of the same     printable document.Masinter, et al.            Standards Track                     [Page 5]

RFC 2534       Media Features for Display, Print, and Fax     March 19992.5 Color and greyscale   - Media Feature tag name(s):   color   - ASN.1 identifier associated with this feature tag:     1.3.6.1.8.1.6   - Summary of the media features indicated by this feature tag:     This feature indicates a gross level of capability to represent (or     need for) for handling of color, out of a limited set of choices.   - Values appropriate for use with this feature tag:     Token with an equality relationship. Values include:     binary      black-and-white, or other bi-level capability.     grey        more than two levels of intensity; for example,                 at least two bits of grey-scale data     limited     availability of a small number of colors, such as                 might be provided by a highlight printer, pen plotter,                 or limited color display. Such capability is useful                 for business graphics. At the lowest level of                 capability, this implies at least one color other than                 black ("highlight color"). At the high end, a small                 number (less than 32) colors. No implication is made                 that any particular color is available.     mapped      pixel color values are mapped in some specifable way                 to a multi-component color space. Sufficient levels of                 display are available to represent a continuous tone                 photographic image, but the result will be mapped into                 a more limited space.     full        ability (or at least willingness) to represent a full                 color image and present it. Full continuous tone color                 capability.   - The feature tag is intended primarily for use in the following     applications, protocols, services, or negotiation mechanisms:Masinter, et al.            Standards Track                     [Page 6]

RFC 2534       Media Features for Display, Print, and Fax     March 1999     Web applications may choose between color, grey, or binary     representations. Fax or printing applications might choose between     color and non-color renditions, for example.   - Examples of typical use:     Someone preparing a map of directions to a restaurant might prepare     different maps for each kind of value.   - Intended usage:     COMMON3. Examples of use of features   The following examples of feature comparison show how these features   can be used to describe various capabilities. The syntax used to   express combinations of features is purely illustrative and not   normative:   pix-x<=1024, pix-y<=768      might be used for a 1024x768 display.   dpi=300      might be used for a 300 dpi printer.   paper-size=a4      indicates the display size is 210x297mm.4. IANA considerations   This document calls for registration of the following feature tags,   as per [REG]: pix-x, pix-y, dpi, ua-media, paper-size, color.  ASN.1   identifiers should be assigned to each of these and replaced in the   body of the registration.5. Security Considerations   Inaccurate media feature information ascribed to a recipient might   cause a sender to subsequently send content that the recipient is not   actually able to process, thus causing a denial of service.6. Acknowledgments   This document is based on a previous memo co-authored with Lou   Montoulli. It had benefited from the comments of Graham Klyne, Ho   John Lee, Brian Behlendorf, Jeff Mogul, Ted Hardie, and Dan Wing.Masinter, et al.            Standards Track                     [Page 7]

RFC 2534       Media Features for Display, Print, and Fax     March 19997. References   [REG] Holtman, K., Mutz, A. and T. Hardie. "Feature Tag Registration         Procedures",BCP 31,RFC 2506, March 1999.   [SI]  ISO 1000:1992 "SI units and recommendations for the use of         their multiples and of certain other units", International         Organization for Standardization, 1992.Authors' Addresses   Larry Masinter   Xerox Corporation   Palo Alto Research Center   3333 Coyote Hill Road   Palo Alto CA 94304   Fax +1 650 812 4333   EMail: masinter@parc.xerox.com   Dan Wing   Cisco Systems, Inc.   101 Cooper Street   Santa Cruz, CA 95060  USA   Phone: +1 831 457 5200   Fax:   +1 831 457 5208   EMail: dwing@cisco.com   Andrew H. Mutz   Jutvision Corporation   124 University Avenue Suite 202   Palo Alto CA 94301   Phone: +1 650 325 6787   Fax:   +1 650 325 9337   Email: mutz@alum.mit.edu   Koen Holtman   Technische Universiteit Eindhoven   Postbus 513   Kamer HG 6.57   5600 MB Eindhoven (The Netherlands)   EMail: koen@win.tue.nlMasinter, et al.            Standards Track                     [Page 8]

RFC 2534       Media Features for Display, Print, and Fax     March 1999Full Copyright Statement   Copyright (C) The Internet Society (1999).  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.Masinter, et al.            Standards Track                     [Page 9]