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

  - 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 1999


2.2 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 1999


2.3 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 1999


2.5 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:

    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: [email protected]


  Dan Wing
  Cisco Systems, Inc.
  101 Cooper Street
  Santa Cruz, CA 95060  USA

  Phone: +1 831 457 5200
  Fax:   +1 831 457 5208
  EMail: [email protected]


  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: [email protected]


  Koen Holtman
  Technische Universiteit Eindhoven
  Postbus 513
  Kamer HG 6.57
  5600 MB Eindhoven (The Netherlands)

  EMail: [email protected]



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]


You are viewing proxied material from gopher.rbfh.de. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.