The testing paradigm applied to network structure

The tcstiny paradiqm provides a simple framework for comparing networks of processes. To apply the testiug paradigm, oue needs a. suite of test.s and a test criterion expressing when a. network passes a tCHt. Two network.s arc cOllsidE:~red testing equivalent when they pa.ss the same tests. In all a.pplications of the testing paradigm that we have seen, tests "probe" (some of) the behavior' of the proc.ess uetwork under test. Network structure, however, is mostly haudled in an ad hoc W(l,Y. In this note, we liSP the t(~st.ing paradigm to compare structural aspects of process networks. Central to onr approach al"(~ the fullowing three ingredients: (i) Tests are drawn from the .set of process lIetworks, that. is, each test, is itself just a process network. (ii) A (global) correctness coneern, iu tlw form of a predicate, expresses when a network is correct as an autouoIllOUS system. (iii) A network pa..:;;ses a test (by another network) when the composition of two lIetworks involved is a correct (autonomous) system. OUf approach ha.<; Hcveral merits. It. allows a uniform treatment of structure and be­ havior. Structural anci hehavioral COrtectlH~s~ (·oucerUR cau be varied independently within the HftlllC framework. Structural correctueHS concerns cau be made explicit at the very beginning, and Heed not appear implicitly a.s an unmotivated afterthought. Several phe­ nomena, such as nondetcrmillislll, cau he illustrated solely in terms of structure, without getting bogged down hy behavioral complic