Interfacing HOL90 with a Functional Database Query Language

We describe a functional database language OR-SML for handling disjunctive information in database queries, its implementation in Standard ML [10], and its interface to HOL90. The core language has the power of the nested relational algebra, and it is augmented with or-sets which are used to deal with disjunctive information. Sets, or-sets and tuples can be freely combined to create objects, which gives the language a greater flexibility. We give an example of queries over the “database” of HOL90 theories which require disjunctive information and show how to use the language to answer these queries. Since the system is running on top of Standard ML and all database objects are values in the latter, the system benefits from combining a sophisticated query language with the full power of a programming language. The language has been implemented as an HOL90-loadable library of modules in Standard ML.