Representing Contextualized Data using Semantic Web Tools
Robert M. MacGregor, In‐Young Ko · 2003
Abstract: RDF-based tools promise to provide a base for reasoning about metadata and about situated data—data describing entities situated in time and space—that is superior to alternatives such as relational databases or object-oriented databases. However, essential representational machinery is missing from the current generation of Semantic Web tools and languages. When that machinery is added, the resulting capabilities offer a combination of novelty and flexibility that may usher in a wave of commercial Semantic Web tool-based applications that precedes the true arrival of the Semantic Web. We have constructed a system, the Semantic Engineering Workbench (SEW), that is proficient at managing situated data. Achieving a practical implementation necessitated extending the basic RDF tools (Hewlett-Packard’s Jena and Stanford’s Protégé) to support contexts. In the SEW, a context references a set of statements having common spatial, temporal (and other metadata) attributes. We investigated multiple possible implementations of contexts, and found significant drawbacks in the most common approaches. The clear winners are quads (adding a fourth field of type ‘context ’ to each triple results in a quadruple, or quad), and object-oriented contexts (a context mechanism that references individuals instead of statements). Most existing Semantic Web tools (e.g., Jena and Protégé) do not understand contextualized data. For these tools, object-oriented