Improving the Usability of HOL Through Controlled Automation Tactics

This paper introduces the concept of controlled automation as a balanced medium between high-level automated reasoning and low-level primitive tactics in HOL. We created a new tactic that subsumes many existing low-level tactics for logical operations and three new tactics that simplify common uses of term rewriting: definition expansion, simplification, and equational rewriting. To implement the tactics, we extended HOL with a facility to label assumptions and operate uniformly on both goals and assumptions. We select automatically and predictably which low-level tactic to apply by examining the structure of the selected assumption or goal. A simple and uniform set of hints enable users to provide the minimal information needed to guide the tactics. We performed two case studies and achieved a 60% reduction in the number of unique tactics used.