Observations About Using Logic as a Specification Language

This extended abstract contains some non-technical observations about the roles that logic can play in the specification of computational systems. In particular, computation-as-deduction, meta-programming, and higher-order abstract syntax are briefly discussed. 1 Two approaches to specifications In the specification of computational systems, logics are generally used in one of two approaches. In one approach, computations are mathematical structures, containing such items as nodes, transitions, and state, and logic is used in an external sense to make statements about those structures. That is, computations are used as models for logical expressions. Intensional operators, such as the modals of temporal and dynamic logics or the triples of Hoare logic, are often employed to express propositions about the change in state. For example, next-time modal operators are used to describe the possible evolution of state; expressions in the Hennessey-Milner are evaluated against the transitions..