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INTERNET-DRAFT                                           Larry Masinter
draft-masinter-media-features-02.txt                       Koen Holtman
                                                              Andy Mutz
                                                               Dan Wing
expires in 6 months                                    January 14, 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
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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 [FEATURES].
This specification does not define a syntax for describing sets of
features.

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 media features [5].  These features are the
means 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), display resolution (in pixels/inch),
color capability and bit-depth, display media type, or . The physical
dimensions of the 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 certain standard paper sizes.

pix-x=n
pix-y=m

  These features indicate the maximum display size that the recipient
  can conveniently display or print, measured in pixels; they indicate
  horizontal (n) and vertical (m) dimensions.

res=nXm

   This feature indicates a discrete resolution in horizontal and
   vertical inch-based units. The characteristic of a resource or
   the capability of a device can be indicated using this feature.
   "n" represents the horizontal resolution, and "y" represents the
   vertical resolution.  Each is measured in integer pixels per inch,
   and the value of res is one discrete token describing both resolutions.
   For example: res=72x72.  Certain resources such as images may have
   similar total pixel size but differing data size, quality, or aspect
   ratio.  Common values of res are:  60x60, 72x72, 100x100, 200x100,
   200x200, 300x300, and 400x400.  Other values may be used.

   Note: While English units are not universal, it is preferable to
   avoid multiple unit definitions.

UA-media=token

   This feature indicates the recipients device media, indicated with
   an simple token.  Basic token values are: screen, stationery,
   transparency, envelope, or continuous-long.  Other values may be
   defined.  Except for "screen" and "Screen-paged", these tokens are
   a subset of the Printer MIB MediaType set defined in RFC-1759 [6].
   Other tokens may be registered and used as needed.

   They are defined as:
     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
     continuous-short: continuously connected sheets of an opaque
                       material connected along the short edge

papersize=token

   For ua-media types such as 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 lieu of
   or in addition to this information.  Paper sizes names and
   definitions are taken from the the Printer MIB RFC [6].

   Examples of paper size tokens, with names from [6], are:
     na-letter:        8.5x11.0 inches
     iso-A4:           210x297 mm
     iso-B4:           250x353 mm
     iso-A3:           297x420 mm
     na-legal:         8.5x14 inches

color=n
grey=n

   The color capabilities of the recipient are indicated with feature
   tag and a parameter describing the number of color channel bits
   available.  Values of n 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.

tiff=p

   The ability to process image/tiff application profiles, defined by [TIFF].
   Image/tiff application profiles are used to indicate subsets of resolution,
   size and coding methods supported by a TIFF application.  Additional
   feature tags describing resolution, media size and so forth may be
   required to completely describe a resource or device.

Examples

   pix-x=1024
   pix-y=768
      indicates a 1024x768 display or a resource best viewed using a
      1024x768 display.

   res=72x72
      indicates a 72 dpi display or a resource intended for use with
      a 72 dpi display.

   UA-media=stationery
      indicates the display is a cut sheet of opaque material, such as
      paper, or a resource intended for use with paper.

   papersize=iso-a4
      indicates the display size is 210x297mm, or the resource is
      intended for output on this display size.

   color=24
      indicates the display supports 24-bit (8-bit/channel) color, or
      a resource intended for display on such a device.

   tiff=F
      indicates a devices supporting tiff-profile F or a resource
      intended for display with such a device.

Acknowledgments

   This document is based on a previous draft co-authored with Lou
   Montoulli, Koen Holtman and Andy Mutz. It had benefited from the
   comments of Ho John Lee, Brian Behlendorf, and Jeff Mogul.

References

   [1]     T.  Berners-Lee.  "Universal Resource Identifiers in WWW." A
   Unifying Syntax for the Expression of Names and Addresses of Objects
   on the Network as used in the World-Wide Web." RFC 1630, CERN, June
   1994.

   [2]     T.  Berners-Lee, L.  Masinter, M.  McCahill.
   "Uniform Resource Locators (URL)." RFC 1738, CERN, Xerox PARC,
   University of Minnesota, December 1994.

   [3]     T.  Berners-Lee, R.  Fielding, H.  Frystyk.
   "Hypertext Transfer Protocol -- HTTP/1.0." RFC 1945." MIT/LCS, UC
   Irvine, May 1996.

   [4]     T.  Berners-Lee, R.  Fielding,I J.  Gettys, J.  Mogul, H.
   Frystyk.   "Hypertext Transfer Protocol - HTTP/1.1"  MIT/LCS,
   UC Irvine, May 1996.

   [5]     K. Holtman, A. Mutz, "Transparent Content Negotiation in HTTP"
   IETF Internet Draft draft-holtman-http-negotiation-04.txt, Nov. 1996.

   [6]     R.  Smith, F.  Wright, T.  Hastings, S.  Zilles, J.  Gyllenskog.
   "Printer MIB." RFC 1759." IETF, March 1995

   [7]     K. Holtman, A. Mutz, "Feature Tag Registration Procedures" IETF
   Internet Draft draft-ietf-http-feature-reg-00.txt, October 1996.


   [ABNF] Crocker, D., and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [MDN-CAPS] Wing, D., and L. Masinter, "Using Message Disposition
        Notifications to Indicate Capabilities", Work in Progress,
        Internet Draft, draft-ietf-fax-mdn-capabilities-00.txt.

   [T.30] ITU-T (CCITT), "Procedures for Document Facsimile Transmission
        in the General Switched Telephone Network", ITU-T (CCITT),
        Recommendation T.30, July, 1996.

   [TIFFREG] Parsons, G., Rafferty, J., and S. Zilles, "Tag Image File
        Format (TIFF) - image/tiff MIME Sub-type Registration", Work in
        Progress, Internet Draft, draft-ietf-fax-tiff-reg-XX.txt.

   (more conneg drafts)

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


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