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 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 learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (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 [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