Testing Concurrent Systems: An Interpretation of Intuitionistic Logic

We present a natural confluence of higher-order hereditary Harrop formulas (HH formulas), Constraint Logic Programming (CLP, [JL87]), and Concurrent Constraint Programming (CCP, [Sar93]) as a fragment of (intuitionistic, higher-order) logic. This combination is motivated by the need for a simple executable, logical presentation for static and dynamic semantics of modern programming languages. The power of HH formulas is needed for higher-order abstract syntax, and the power of constraints is needed to naturally abstract the underlying domain of computation. Underpinning the combination is a sound and complete operational interpretation of a two-sided sequent presentation of (a large fragment of) intuitionistic logic in terms of behavioral testing of concurrent systems. Formulas on the left hand side of a sequent style presentation are viewed as a system of concurrent agents, and formulas on the right hand side as tests against this evolving system. The language permits recursive definitions of agents and tests, allows tests to augment the system being tested and allows agents to be contingent on the success of a test. We present a condition on proofs, operational derivability (OD), and show that the operational semantics generates only operationally derivable proofs. We show that a sequent in this logic has a proof iff it has an operationally derivable proof.