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rfc:rfc2534

Network Working Group L. Masinter Request for Comments: 2534 Xerox Corporation Category: Standards Track D. Wing

                                                 Cisco Systems, Inc.
                                                             A. Mutz
                                               Jutvision Corporation
                                                          K. Holtman
                                                                 TUE
                                                          March 1999
             Media Features for Display, Print, and Fax

Status 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

  1. Media Feature tag name(s):
   pix-x
   pix-y
  1. ASN.1 identifier associated with this feature tag:
   1.3.6.1.8.1.1
   1.3.6.1.8.1.2
  1. 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.
  1. Values appropriate for use with this feature tag:
   Signed Integer
  1. 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 1999

2.2 Resolution

  1. Media Feature tag name:
   dpi
  1. ASN.1 identifier associated with this feature tag:
   1.3.6.1.8.1.3
  1. 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.
  1. Values appropriate for use with this feature tag:
   Rational
  1. 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.
  1. Examples of typical use:
   Choosing a version of a printable document to send to a printer.
  1. 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 1999

2.3 Registration of 'ua-media'

  1. Media Feature tag name(s):
   ua-media
  1. ASN.1 identifier associated with this feature tag:
   1.3.6.1.8.1.4
  1. Summary of the media features indicated by this feature tag:
   This feature indicates the recipients device media, indicated with
   an simple token.
  1. 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
  1. 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.
  1. 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.
  1. 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

  1. Interoperability considerations:
   Interoperability with the Internet Print Protocol means that some
   additional feature values may need to be registered.

2.4 Paper Size

  1. Media Feature tag name(s):
   paper-size
  1. ASN.1 identifier associated with this feature tag:
   1.3.6.1.8.1.5
  1. 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.
  1. 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
  1. 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.
  1. 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 1999

2.5 Color and greyscale

  1. Media Feature tag name(s):
 color
  1. ASN.1 identifier associated with this feature tag:
   1.3.6.1.8.1.6
  1. 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.
  1. 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.
  1. 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.
  1. Examples of typical use:
   Someone preparing a map of directions to a restaurant might prepare
   different maps for each kind of value.
  1. Intended usage:
   COMMON

3. 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 1999

7. 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.nl

Masinter, et al. Standards Track [Page 8] RFC 2534 Media Features for Display, Print, and Fax March 1999

Full 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]

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