We have presented a formalization of STRIPS as a reasoning strategy in the situation calculus. In doing so, we have proposed and illustrated a conceptual framework for the declarative formalization of reasoning strategies consisting of mental situations, mental actions, and heuristics. Declarative formalizations of reasoning strategies have a number of advantages. One of them is that they can be improved by simple additions of better heuristics  . For example, axioms , and describe the heuristics used for determining which actions are appropriate for achieving a subgoal, ordering actions, and detecting dead-ends during the searching process. We can enhance the reasoning strategy formalized in the paper by simply adding new disjuncts describing better heuristics to the right hand side of any of those axioms.
The author would like to thank John McCarthy for introducing her into the idea of the mental situation calculus, suggesting the problem of the declarative formalization of reasoning strategies, and providing valuable ideas, comments and help whenever they were needed. Luc Steels encouraged and enriched the writing of this paper with valuable ideas. Mike Genesereth read carefully a previous version of the paper, and contributed with valuable comments. John McCarthy, Tom Costello, Eyal Amir and Aarati Parmar participate in useful discussions that helped to shape the final version of the paper. This work was supported partly by the Navy Grant N00014-94-1-0775, and partly by the Air Force Grant F49620-97-1-0207.