Focusing on Traces to Link VCR and CSP
Marc L. Smith · 2004
View-Centric Reasoning (VCR) replaces CSP's (1) perfect observer with multiple, possibly imperfect observers. To employ view-centric reasoning within ex- isting CSP models (2) requires a bookkeeping change. Specifically, VCR (3) intro- duces parallel events as a new primitive for constructing traces, and distinguishes two types of traces: histories and views. Previously, we gave the operational semantics of VCR (4), and demonstrated the utility of parallel traces to reason for the first time un- ambiguously about the meaning of the Linda predicate operationsrdp() andinp(). The choice of using an operational semantics to describe VCR makes direct compari- son with CSP difficult; therefore, work is ongoing to recast VCR denotationally, then link VCR with the other CSP models within Hoare and He's Unifying Theories of Programming(5). Initial efforts in this direction (6) led to a comparison of VCR with Lawrence's HCSP (7). In this paper, we present some recent insights and abstractions - inspired by modern quantum physics - that have emerged whilst contemplating par- allel traces in light of the unifying theories. These insights lead to a more natural expression of VCR traces, in the sense that they more closely resemble CSP traces, thus forming a basis for linking VCR and CSP.