An ontology-extended relational algebra

Heterogeneous relational databases being integrated vary widely in how the same data is represented. We propose the notion of an ontology extended relation (OER). An OER contains an ordinary relation as well as an associated ontology that conveys semantic meaning about the terms being used. We extend the relational algebra to query OERs. The advantage of this is that the OER model can be directly built on top of commercial relational DBMSs. We describe an implementation of the OER model and show (via experiment) that the system scales to handle large data sets.