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INTERNET-DRAFT                                          Larry Masinter
draft-ietf-conneg-media-features-01.txt                   Koen Holtman
                                                             Andy Mutz
                                                              Dan Wing
expires in 6 months                                      Aug 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,
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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 [REG].

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 certain
standard paper sizes.  These are presented formally in the Notation
section.

pix-x (integer)
pix-y (integer)

  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.

dpi (integer)

  This feature indicates a resolution that the recipient can display
  or print without loss, measured in pixels per inch; resolution is
  typically represented as 'dpi' (dots-per-inch) rather than in SI
  units [SI]; however 254 dpi is equivalent to 100 dots per centimeter.

media (token)

  This feature indicates the recipients device media, indicated with
  an simple token.  All (except for "screen" and "screen-paged") are
  taken from the Printer MIB MediaType set defined in RFC 1759
  [PRINTMIB].  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
        envelope-plain   Envelopes that are not preprinted and have no
                         windows
        envelope-window  Envelopes that have windows for addressing
                         purposes
        continuous-long  Continuously connected sheets of an opaque
                         material connected along the long edge
        continuous-short Continuously connected sheets of an opaque
                         material connected along the short edge
        tab-stock        Media with tabs
        multi-part-form  Form medium composed of multiple layers not
                         pre-attached to one another; each sheet may be
                         drawn separately from an input source
        labels           Label stock
        multi-layer      Form medium composed of multiple layers which
                         are pre-attached to one another; e.g., for
                         use with impact printers"

papersize (token)

   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.)  Paper
   sizes names and definitions are taken from RFC 1759 [PRINTMIB],
   which in turn imported the definitions from ISO/IEC 10175.

   Examples of paper size tokens, with names from [MIB], 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 (integer)
grey (integer)

   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 (token)

   The ability to process Internet Media type image/tiff [TIFF]
   extension FX profiles corresponding to the given token. [RFC2301] defines
   several such profiles: S, F, J, C, L, M.  Others may be registered
   with IANA as part of an extension to the TIFF feature set.

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

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

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

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

   papersize=na-letter,dpi<=200,tiff=S
      might be used for a fax machine with 'simple mode'.
   papersize=na-letter,dpi<=400,tiff={S,F,C,M}
      might be used for a fax machine with enhanced capabilities.

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

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

   [REG] K. Holtman, A. Mutz. "Feature Tag Registration Procedures",
        draft-ietf-conneg-feature-reg-00.txt, March 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.

   [TIFF] Parsons, G., Rafferty, J., and S. Zilles, "Tag Image File
        Format (TIFF) - image/tiff MIME Sub-type Registration".
        RFC 2302, March 1998.

   [RFC2301] L. McIntyre, S. Zilles, R. Buckley, D. Venable, G.
        Parsons, J. Rafferty, "File Format for Internet Fax".
        RFC 2301, March 1998.

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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