Wednesday, April 23, 2008

Semantic Data Storage

Since we had another lecture delving into the semantic web I thought I would talk about some semantic web technologies, like oracle 11g. The approach oracle takes is to use their existing database technology and augment it to support owl constructs and inferencing. Oracle 11g holds a table for each semantic model, the structure of these tables is always the same. These data tables have 3 columns, one for each part of the triple, in addition to these 3 columns they have columns to provide a unique identifier to triples, a column to link back to the model this triple belongs to, and a bunch of columns that are reserved for future use. Oracle 11g automatically maintains views for what tables belong to what data models, and a view for triples associated with models along with other views.

Oracle 11g supports inferencing using rules and rulebases. Rules are basically if then statements, and rulebases are their containers (implemented with tables). Oracle 11g comes with a set of common rulebases for RDF (and variants) and OWL. Rules can be created and inserted into rulebases. Inferencing is further supported with rule indices that hold precomputed values for rules. Oracle 11g also provides functions like SEM_MATCH and SEM_DISTANCE.

If this brief overview has wet your appetite, check out for more.

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