One document matched: draft-masinter-media-features-01.txt

Differences from draft-masinter-media-features-00.txt

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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].

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.
These are presented formally in the Notation section.
    
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<=n
    
   This feature indicates the maximum resolution that the recipient
   can display or print without loss, measured in pixels per inch.
   For example: res<=72.  Certain resources such as images may have
   similar total pixel size but differing data size and quality
   depending on degree of compression.
     
   Note: While English units are not universal, it is preferable to
   avoid multiple unit definitions. Equivalent metric definitions
   are available.
    
res-x<=n
res-y<=m

   In cases where non-square aspect ratio is supported, these
   features can be used for specifying horizontal and vertical resolution
   capabilities.

res=nXm
   A recipient which has fixed set of resolutions available may instead
   indicate its capabilities by indicating the resolution(s) it can
   support.


UA-media=token  
    
   This feature indicates the recipients device media, indicated with
   an simple token.  Basic token values are: screen, stationary,
   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 
     stationary:       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 stationary, 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].
   If additional feature tags are given for describing resolution, media
   sizes and so forth, they are added to those application profiles.

Examples    

   pix-x<=1024 
   pix-y<=768 
      indicates a 1024x768 display 
    
   res<=72  
      indicates a 72 dpi display  
    
   UA-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,res-x={204,200,300},
     res-y={98,196,100},tiff=F

   papersize=na-letter,res={200x98,200x196,200x100},tiff={M,J}

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