From Sequential Processes to Grid Computation

We introduce an extended model for view-centric reasoning, EVCR, that provides more comprehensive and flexible abstractions for representing actual concurrency. The theory of Communicating Sequential Processes (CSP) provides an interleaved semantics for reasoning about concurrency through a sequentialized trace of events recorded by an idealized observer. The theory of View-Centric Reasoning (VCR) extended CSP with notions of parallel events and views, and lazy observation, to represent the true concurrency of simultaneous events and multiple, possibly imperfect observers. But VCR could be more general still, since its events, like those of CSP, are instantaneous. This restriction precludes the possibility of observing events that partially overlap in time. EVCR permits partially overlapping events to be observed and recorded by a lazy observer. The result is a more general model of concurrency; one that is more appropriate for reasoning about network functioning and, in particular, grid computation.