Myrtle: A Set-Oriented Meta-Interpreter Driven by a “Relational” Trace for Deductive Databases Debugging

Abstract

Deductive databases manage large quantities of data and, in general, in a set-oriented way. The existing explanation systems for deductive databases [6,4,1] give information in the shape of forests of proof trees. Although proof trees are often useful, this representation is not sufficient. We propose a tracing technique which consists of integrating a ”relational” trace and an instrumented meta-interpreter using substitution sets. The relational trace efficiently gives precise information about data extraction from the relational database. The meta-interpreter manages substitution sets and gives explanation on the deduction. The expensive aspects of meta-interpretation are reduced by the use of the trace which avoids many calculations. The flexibility of meta-interpretation is preserved. It allows different profiles of trace to be easily produced.