Refinement checking and FDR
	n The notion of refinement n The implementation should be a refinement of the specification, in the sense of preserving its properties. Hence, less nondeterministic n Refinement checking: checking that the implementation is indeed a refinement of the specification n Obviously, the notion of refinement depends on the intended semantic. In CSP traditionally we consider 3 kinds of semantics: n Traces n Failures n Failures and Divergences