Swoogle knows how Semantic Web ontologies are used

April 4th, 2006

The Dublin Core Metadata Initiative is updating the RDF expression of DC and might add range restrictions to some properties. Mikael Nilsson wondered if we would use the Swoogle Semantic Web search engine to see what types of values are being used with DC properties.

This kind of query is just the ticket for Swoogle. Well, almost. The current web-based interface supports a limited number of query types. Many more can be asked if you use SQL directly to query Swoogle’s underlying databases. We don’t want to provide a direct SQL query service over the main Swoogle database because it’s easy to ask a query that will take a looooooong time to answer and some could even crash the database server. We are planning to put up a second server with a copy of the database and we give Swoogle Power Users (SPUs) access to it.

We ran a simple SQL query to generate some initial data for Mikael showing fall of the DC properties. For each one, we list all of the ranges that values were drawn from and the number of separate documents and triples for each combination. For example

Property
Range
Documents
Triples
dc:creater rdfs:Literal
32
648
dc:creator rdfs:Literal
234655
2477665
dc:creator wn:Person
2714
1138250
dc:creator cc:Agent
4090
6359
dc:creator foaf:Person
2281
5969
dc:creator foaf:Agent
1723
3234

Notice that the first property in this partial table is an obvious typo. You can see the complete table as pdf file or as an excel spreadsheet.