Abstract Views of Prolog Executions in Opium

Opium is a system for analysing and debugging Prolog programs. Its kernel comprises an execution tracer and a programming language with a set of primitives for trace and source analysis. In this report we show the power of Opium for supporting abstract views of Prolog executions. Abstract views give high-level points of view about executions. They filter out irrelevant details; they restructure the remaining information; and they compact it so that the information given at each step has a reasonable size. The examples of abstract views given in the following are a goal execution profile, some data abstractions, an instantiation profile, a failure analysis, a loop analysis, and a kind of explanation for an expert system written in Prolog