[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 RFC 2534

INTERNET-DRAFT                                          Larry Masinter
draft-ietf-conneg-media-features-02.txt                   Koen Holtman
                                                             Andy Mutz
                                                              Dan Wing
expires in 6 months                                  September 7, 1998

              Media Features for Display, Print, and Fax

Status of this memo

   This document is an Internet-Draft. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time.  It is inappropriate to use Internet-Drafts
   as reference material or to cite them other than as "work in
   progress."

   To view the entire list of current Internet-Drafts, please check
   the "1id-abstracts.txt" listing contained in the Internet-Drafts
   Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net
   (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au
   (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu
   (US West Coast).

   Copyright (C) The Internet Society (1997).  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.

   Media features may be used in many different protocol situations.
   Those defined in this specification can indicate the display or
   printer dimensions (in pixels), color capability and bit-depth, or
   media type.  The physical dimensions of a display can 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:

     ***New assignments by IANA***

   - 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.

2.2 Resolution

   - Media Feature tag name:

     dpi

   - ASN.1 identifier associated with this feature tag:

     ***New assignments by IANA***

   - 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.

2.3 Registration of 'media'
   - Media Feature tag name(s):

     ua-media

   - ASN.1 identifier associated with this feature tag:

     ***New assignments by IANA***

   - 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. Typical 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.

   - 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:

     ***New assignment by IANA***

   - 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:
     String with equality

     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.

2.5 Color and greyscale
   - Media Feature tag name(s):

     color
     grey

   - ASN.1 identifier associated with this feature tag:

     ***New assignments by IANA***

   - Summary of the media features indicated by this feature tag:

     The color capabilities of the recipient are indicated with
     feature value describing the number of color (or greyscale)
     channel bits available.

   - Values appropriate for use with this feature tag:

     Integer

     Values are typically (but not limited to) 2, 8, or 24.  For
     example: grey=8 indicates a display capable of representing an
     image in 256 levels of a single color, while color=8 indicates a
     display capable of representing an image with a palette of 256
     colors.

   - The feature tag is intended primarily for use in the following
     applications, protocols, services, or negotiation mechanisms:

     Web applications may choose between color, greyscale, or binary
     representations. Fax applications may choose between color
     and non-color renditions.

   - Examples of typical use:

     n/a

   - Related standards or documents:

     n/a

   - Considerations particular to use in individual applications,
     protocols, services, or negotiation mechanisms:

     n/a

   - Interoperability considerations:

     n/a

   - Security considerations:

     n/a

   - Privacy concerns, related to exposure of personal information:

     n/a

   - Denial of service concerns related to consequences of specifying
     incorrect values:

     n/a

   - Additional information:

     n/a

   - Keywords:

     n/a
   - Related feature tags:


   - Related media types or data formats:


   - Related markup tags:


   - Name(s) & email address(es) of person(s) to contact for
     further information:


   - Intended usage:
     COMMON

   - Author/Change controller:


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
      indicates a 1024x768 display

   dpi<=72
      indicates a 72 dpi display

   ua-media=stationery
      indicates the display is a cut sheet of opaque material, such as
      paper.

   paper-size=iso-a4
      indicates the display size is 210x297mm.

   color<=24
      indicates the display supports 24-bit (8-bit/channel) color.

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, grey,
   ASN.1 identifiers should be assigned to each of these and replaced
   in the body of the registration.

4. Acknowledgments

   This document is based on a previous draft co-authored with Lou
   Montoulli. It had benefited from the comments of Graham Klyne, Ho
   John Lee, Brian Behlendorf, Jeff Mogul, and Ted Hardie.

References

   [REG] A. Mutz, T. Hardie. "Feature Tag Registration Procedures",
        draft-ietf-conneg-feature-reg-03.txt, July 1998.

   [SI] ISO 1000:1992 "SI units and recommendations for the use of
        their multiples and of certain other units", International
        Organization for Standardization, 1992.

Author's Addresses

   Larry Masinter
   Xerox Palo Alto Research Center
   3333 Coyote Hill Road
   Palo Alto CA 94304
   Fax +1 415 812 4333
   Email: masinter@parc.xerox.com

   Dan Wing
   Cisco Systems, Inc.
   101 Cooper Street
   Santa Cruz, CA 95060  USA
   Phone: +1 408 457 5200
   Fax:   +1 408 457 5208
   EMail: dwing@cisco.com

   Andrew H.  Mutz
   Hewlett-Packard Company
   1501 Page Mill Road 3U-3
   Palo Alto CA 94304, USA
   Fax +1 415 857 4691
   Email: mutz@hpl.hp.com

   Koen Holtman
   Technische Universiteit Eindhoven
   Postbus 513
   Kamer HG 6.57
   5600 MB Eindhoven (The Netherlands)
   Email: koen@win.tue.nl


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/