A fine-grained modality classification for global predicates

Abstract

Specifying and detecting predicates in a distributed execution is an important problem. Distributed execution observation has classically used two modalities-Possibly(/spl Phi/) and Definitely(/spl Phi/)-for predicate /spl Phi/. Based on the temporal interactions of intervals, the author identified a complete, orthogonal set of relationships /spl Rfr/; between pairs of intervals in a distributed execution. We show how to map the rich, orthogonal classification of modalities of pairwise interval interactions, to the classical coarse-grained classification, Possibly(/spl Phi/) and Definitely(/spl Phi/), for specifying predicates defined on any number of processes. This increases the power of expressing the temporal modalities under which predicates can be specified, beyond the current Possibly/Definitely classification. We give some timestamp-based tests for the orthogonal modalities in the refined classification.