SQOWL: Performing OWL-DL type inference in SQL

In this report we describe a method to perform type inference over data stored in an RDBMS, where rules over the data are specified using OWL-DL. Since OWL-DL is an implementation of the Description Logic (DL) SHOIN (D), we are in effect implementing a method for SHOIN (D) reasoning in relational databases. Reasoning make be broken down into two processes of classification and type inference. Classification may be performed efficiently by a number of existing reasoners, and since classification alters the schema, it need only be performed once for any given relational schema as a preprocessor of the schema before creation of a database schema. However, type inference needs to be performed for each data value added to the database, and hence needs to be more tightly coupled with the database system. Previously, no technique has been proposed that implements SHOIN (D) type inference within an RDBMS. We propose such a technique, involving the use of triggers to perform reasoning over the data values as they inserted into the database. We demonstrate the soundness and performance of our approach by comparing an implementation of our technique against other existing approaches for less powerful reasoning over data in an RDBMS. The results show we provide the fastest query processing of any technique, despite having a more powerful reasoner.