[Mirrored from: http://www.ukc.ac.uk/library/ICCC/rutledge]

ICCC/IFIP Conference: Electronic Publishing '97
New Models and Opportunities

14-16 April 1997 - University of Kent at Canterbury

Conference Paper Abstract

Hypermedia Generic Structure and Presentation Specification

Lloyd Rutledge, Jacco van Ossenbruggen, Lynda Hardman, Dick C.A. Bulterman, Anton Eliens

We describe the process of determining the presentation-independent hypermedia structure of a hypermedia document, using an existing document format as an example. We also propose a mechanism for the specification of the processing of hypermedia structure for presentation.

SGML is a widely used ISO standard for text document structuring because of its support for document exchange, reuse and longevity. It represents a document in its permanently stored form, but does not define its processing into any presentation. SGML also provides for the defining of separate document sets.

The Document Style Semantics and Specification Language (DSSSL) provides a system-independent way to describe the processing of SGML documents of a given set into various forms of text-based output. DSSSL specifies this formatting process by defining a powerful document query language, a document transformation language and a style language to apply a set of formatting characteristics to portions of the document.

The HyTime standard builds upon and extends SGML presentation-independent structuring from text into hypermedia. This structure includes complex hyperlinking, locating of document objects, and the scheduling of objects within measured coordinate systems such as space and time. Portability and reuse of information is further enhanced by allowing HyTime documents to include portions of other documents, even ones from other document sets.

The CWI Multimedia Interchange Format (CMIF) encodes hypermedia documents for presentation on a variety of platforms. The interface features of these presentations include the placement of media items on a screen and along a timeline. Hyperlinks can be defined among different portions of the document. As a multi-platform format, CMIF defines its documents in a flexible manner that can be processed for presentation in a variety of circumstances. To facilitate CMIF's processing for multiple environments, we have defined the format as a HyTime document set.

HyTime, like SGML, requires external mechanisms for specifying the presentation of its document. DSSSL's style language is suited primarily for formatting hypertext documents for printing on paper or display by a page-based browser. It does not support the scheduling and synchronization of time-based hypermedia fragments, such as audio, video and (3D) animation. While text documents tend to display a relatively sharp boundary between logical structure and physical layout, this distinction is less clear when hypermedia documents are concerned..

This paper presents our use of HyTime structuring and DSSSL presentation formatting with CMIF and the issues involved. First, we describe the process of determining the presentation-independent hypermedia structure of CMIF and its HyTime encoding. This process and its issues are applied to the HyTime encoding of existing hypermedia formats in general. Second, we propose a style sheet formalism which builds upon the DSSSL and HyTime standards allowing authors to specify the processing of hypermedia structure for presentation. We conclude by describing the unified environment that incorporates both these processes.

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