Flexible Design and Efficient Implementation of a Hypermedia Document Database System by Tailoring Semantic Relationships

Abstract

In this paper we present the design concepts and data modeling approach that was used to define a general application framework for storing hypermedia documents in the object-oriented database management system VODAK. We exploit the capabilities of the VODAK data model to introduce new hypermedia modeling primitives at the meta level. We show that representing the hypermedia semantics within the DBMS in this way is clearly advantageous for efficiency of the design and implementation of hypermedia document storage engines. As an example, we give a concrete realization of a DBMS-based hypermedia engine for the SEPIA hypermedia authoring system developed at GMD-IPSI. With this example we show that the data model extensions provided are flexible enough to represent also complex semantic hypermedia concepts, that the development cycle of a hypermedia engine can become extremely fast and that the resulting implementation has adequate performance for interactive applications.

Classification Based Navigation and Retrieval for Picture Archives

“…Many authors [26,7] refer to the use of semantic networks or term classification systems to underlie hypertext linking or to support the typing of documents and links [26]. Others refer to the implementation of hypermedia systems in an object-oriented model, for example HyperStorM [39] and Multicard [10].…”

Transactional Support for Cooperative Applications

“…The type of the link is determined by type, e.g., two content nodes can be linked by a RefersTo link. For a complete list of link types available in SEPIA and constraints defined on the types, see [TW95a,WA95]. The object identifier of the new link is returned.…”

“…Type specifies the type of hypermedia node, e.g., a ContentNode representing document content, Issue for a problem to be solved, or Position for an author's position. For a complete list of node types in SEPIA see[TW95a,WA95]. The object identifier of the new node is returned.…”

HyperStorM

“…In the following we explain the basic semantic relationships shortly. For a detailed formal description we refer the reader to [28]. Flat hypermedia structures.…”

“…In the simplest case, a flat hypermedia structure can be viewed as a graph consisting of nodes and binary (directed and bidirectional) links. Because we also allow links to refer to other links we extend the definition of graphs by means of a recursive definition of structures that allow links connected to links (R1.2), links connected to links that themselves connect links and so forth (a precise mathematical definition is given in [28]). Most hypermedia systems prohibit loops and dangling links to achieve wellformed hypermedia documents.…”