Partial Model Checking ( Extended

A major obstacle in applying finite-state model checking t o the verification of large systems is the combinatorial explosion of the state space arising when m a n y loosely coupled parallel processes are considered. T h e problem also known as the state-explosion problem has been attacked from various sides. This paper presents a new approach based o n partial model checking: Parts of the concurrent system are gradually removed while transforming the specification accordingly. W h e n the intermediate specifications constructed an this manner can be kept small, the stateexplosion problem i s avoided. Experimental results with a prototype implemented in Standard ML, shows that for Milner’s Scheduler an often used benchmark this approach improves o n the published results o n Binary Decision Diagrams and is comparable to results obtained using generalized Decision Diagrams. Specifications are expressed in a variant of the modal p-calculus.