February 1, 2004
February 1, 2004
Best Practices Document
The Printer Working Group
Status: Approved
In traditional printing environments, clients rely on font downloads when they are not sure a given character is embedded in the printer. As printing moves to small clients, downloading may not be an option and clients have a need to know what characters are available in a given device.
There are many published named character repertoires, and a small client will not know about them all.
[RS] describes the syntax and semantics for the Semantic Model element "RepertoireSupported". The current document describes Best Practices for the use of that element, in order to maximize interoperability between client devices and printers.
The reader of this document should be familiar with the terminology and concepts in [RS].
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Title:
Best Practices for use of the RepertoireSupported Element
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About the Printer
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The Printer Working Group (or PWG) is a Program of the
IEEE-ISTO. All references to the PWG in this document implicitly mean “The
Printer Working Group, a Program of the IEEE ISTO.” The PWG is chartered to make printers and the applications
and operating systems supporting them work together better. In order to meet
this objective, the PWG will document the results of their work as open
standards that define print related protocols, interfaces, data models,
procedures and conventions. Printer manufacturers and vendors of printer related
software would benefit from the interoperability provided by voluntary
conformance to these standards.
In general, a PWG standard is a
specification that is stable, well understood, and is technically competent, has
multiple, independent and interoperable implementations with substantial
operational experience, and enjoys significant public support.
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All sections of this document are normative unless noted as informative.
[RS] describes a syntax for referring to a wide range of character repertoires. In order to promote interoperability, this document designates a small number of repertoires as "well-known". In this way a print client that only knows the names of the well-known repertoires can get useful results.
The repertoires designated as well-known are:
A conforming printer should support and advertise a well-known repertoire whenever it advertises similar repertoires. For example, any printer advertising any Cyrillic repertoire should also advertise "unicode_cyrillic". In this way a client that does not recognize a large number of repertoires can still recognize that some form of Cyrillic printing is possible on this device.
Printers will often support larger repertoires. If a printer supports a repertoire that is a superset of a well-known repertoire, then it should advertise the well-known repertoire in addition to the superset. Examples:
A conforming printer should follow these rules:
Printing protocols (outside of this document) specify how a print client learns about the supported repertoires in a printer. [RS] describes how to determine which characters are supported in each supported charset.
Once it knows, a client may choose to use this knowledge in any of these ways: