What Is HyTime?

  • An ISO/IEC standard: 10744:1997, Hypermedia/Time-based Structuring Language.
  • A mechanism for encoding hyperlinks and other multimedia structures in XML documents.
  • Enables association of metadata with a link.
  • Enables creation of links that reside in a location separate from the linked resources ( extended links ).
  • Enables creation of both unidirectional and bi-directional links.
  • Enables creation of links among more than two resources.
  • Enables linking of anything to anything (not just XML-to-XML).
  • A way to do sophisticated, indirect addressing.


Information Management

  • Enables management of links during authoring through use of indirect addressing.
  • Provides standard syntax and semantics for hyperlink representation.
  • Can define links over information in any format, including linking XML to non-XML data and non-XML data to non-XML data.
  • Can be directly translated to Xlink for online delivery.

Application Maintenance

  • Eliminates need to reinvent linking structures for XML document types.
  • Applications can use generic HyTime processors to support link processing.

How HyTime Works:

HyTime is an application of SGML/XML. In simple terms, HyTime defines a set of element types that you can use with your existing XML document types to provide hyperlinking and other facilities in a standardized way.

In other words, HyTime effectively extends XML by defining a standard set of facilities for doing hypertext and multimedia presentations.

HyTime does not compete with or change XML in any way—it simply builds on the basic facilities XML provides. In particular, HyTime provides the following hypertext-related facilities:

  1. A general model of hyperlinks and syntax for hyperlink representation using XML elements. This is much more than simple ID/IDREF or HTML <A> links.

  2. Facilities for addressing things other than elements with IDs in the local document: cross-document ID refs, references to elements without IDs, references to data characters, or references to multiple objects at once.

These are facilities that all hypertext applications need. HyTime provides a general and robust mechanism for adding them to SGML documents and SGML processing applications. HyTime can also be integrated with other mechanisms, such as HTTP URLs and XPointers.

Technically, HyTime is an "enabling architecture". In particular, rather than defining element types that must be used directly in a DTD, it provides a set of "meta-element types" that serve as templates or supertypes from which element types are derived with their own element type names and specialized attributes. As long as the element types conform to the minimum requirements of the HyTime-defined meta-element types ("architectural forms"), a HyTime-aware processor will be able to provide HyTime-related services, such as finding the anchors of hyperlinks.

HyTime is similar to XLink. They both provide essentially the same linking structures and semantics. The primary difference between HyTime and XLink, besides a few unimportant syntax differences, is that XLInk does not provide any form of indirect addressing, while HyTime provides a rich set of indirect addressing mechanisms. This difference is a direct result of XLink's design for Web delivery—in Web delivery, indirect addressing would be, at best, very expensive to process, and in some cases impossible. This lack of indirection makes it difficult to use XLink for authoring because link management mechanisms depend on indirection. This suggests that HyTime is most appropriate for authoring systems, while Xlink is most appropriate for Web-based delivery. Because HyTime and XLink have essentially identical abstract linking models, it is relatively easy to translate from HyTime based links to XLink-based links.



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