The Role of Intensional and Extensional Representations in Simulation

Abstract

I review three systems which do simulation in different domains. I observe the following commonality in the representations underlying the simulations: • The representations used for individuals tend to be domain-dependent. These representations are highly structured, concentrating in one place all the information concerning any particular individual. I call these representations intensional because two such representations are considered equal if their forms are identical. • With important exceptions, the representations used for classes of individuals tend to be domain-independent. These representations are unstructured sets of predications involving the characteristics of class members. I call these representations extensional because two such representations are considered equal if the classes they specify are identical. I draw out various ramifications of this dichotomy, and speculate as to its cause. In conclusion, I suggest research into the process of debugging extensional class representations and the development of intensional ones.