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