Safety, liveness and run-time refinement for modular process-aware information systems with dynamic sub processes

Abstract

We study modularity, run-time adaptation and refinement under safety and liveness constraints in event-based process models with dynamic sub-process instantiation. The study is part of a larger programme to provide semantically well-founded technologies for modelling, implementation and verification of flexible, run-time adaptable processaware information systems, moved into practice via the Dynamic Condition Response (DCR) Graphs notation co-developed with our industrial partner. Our key contributions are: (1) A formal theory of dynamic subprocess instantiation for declarative, event-based processes under safety and liveness constraints, given as the DCR* process language, equipped with a compositional operational semantics and conservatively extending the DCR Graphs notation; (2) an expressiveness analysis revealing that the DCR* process language is Turing-complete, while the fragment corresponding to DCR Graphs (without dynamic sub-process instantiation) characterises exactly the languages that are the union of a regular and an omega-regular language; (3) a formalisation of run-time refinement and adaptation by composition for DCR* processes and a proof that such refinement is undecidable in general; and finally (4) a decidable and practically useful sub-class of run-time refinements. Our results are illustrated by a running example inspired by a recent Electronic Case Management solution based on DCR Graphs and delivered by our industrial partner. An online prototype implementation of the DCR* language (including examples from the paper) and its visualisation as DCR Graphs can be found at http://tiger.itu.dk:8020/.