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3.3 HyTime

The Hypermedia/Time-based Structuring Language or HyTime is and International Standard for representing hypertext links, and synchronization of static and time-based information contained in multiple conventional and multimedia documents and information objects [SIGLINK, 1992]. It addresses the limitations of SGML [Newcomb et al., 1991]. HyTime supports cross-referencing facilities to uniquely identified elements in external documents. It also extends SGML’s reference capability to accommodate elements with no unique identifiers in the same document. It provides pointers or location addressing schemes that contain the necessary information in order to locate cross-referenced data. It is independent of data content notations, link types, processing, presentation, and semantics. HyTime supports addressing by name, by position in the document, and by semantic construct. Links can be established to documents that conform to HyTime as well as those that do not.

HyTime allows all kinds of multimedia and hypertext technologies (whether proprietary or not) to be combined in any information producs. It addresses only the issue of interchange of hypermedia information and not the standardization of presentation (same as SGML), user interfaces, query languages etc. Objects in a HyTime hypertext document can include formatted and unformatted documents, audio and video segments, still images, animations, and graphics.

HyTime is an SGML application conforming to ISO 8879. It provides the notion of “Architectural Form” to SGML. An architectural form is a syntax template around which a document author can build semantic constructs for linking and coordinate space addressing. It is highly flexible and extensible. The interchange format can be defined in Abstract Syntax Notation 1 (ISO 8824) and can be encoded according to the basic encoding rules of ISO 8825 for interchange using protocols conforming to the OSI model. The full set of HyTime functionality supports “integrated open hypermedia”, the “bibliographic model” of hyperlinking that allows links to anything, anywhere, anytime.

HyTime is intended for use as the infrastructure of platform-independent information exchange for hypermedia and synchronized and non-synchronized multimedia applications. Application developers will use HyTime constructs to design their information structures and objects and the HyTime language to represent them for interchange [SIGLINK, 1992].