   The formalization of temporal reasoning, and in particular of reasoning about actions and plans, is the best-developed successful extension of modern formalization techniques to domains other than mathematical theories.  This departure has required the creation of new methodologies.  One methodological innovation will emerge in  Section 4.5: the development of a library of scenarios for testing the adequacy of various formalisms, and the creation of specialized domains like the blocks-world domain (mentioned above, in Section 4.2) that serve a laboratories for testing ideas.  For more on the blocks world, see  Genesereth &amp; Nilsson 1987;  Davis 1991.  McCarthy’s ideas about elaboration tolerance McCarthy 1999  provide one interesting attempt to provide a criterion for the adequacy of formalizations. Another idea that has emerged in the course of formalizing common sense domains is the importance of an explicit ontology; see, for instance,  Fikes 1996 and  Lenat &amp; Guha 1989.  Another is the potential usefulness of explicit representations of context; see  Guha, 1991.   Another is the use of simulation techniques: see, for instance,   Johnstone &amp; Williamson 2007 