Verification of Hierarchical Artifact Systems

TL;DR

This paper advances artifact verification by modeling complex, realistic workflows with hierarchy, concurrency, and data constraints, proving decidability and analyzing complexity with novel techniques.

Contribution

It introduces a richer, more realistic artifact model incorporating hierarchy, concurrency, and data dependencies, and establishes decidability and complexity results for verification.

Findings

Verification is decidable for the proposed model.

The complexity of verification is characterized.

Novel techniques include a hierarchy of Vector Addition Systems.

Abstract

Data-driven workflows, of which IBM's Business Artifacts are a prime exponent, have been successfully deployed in practice, adopted in industrial standards, and have spawned a rich body of research in academia, focused primarily on static analysis. The present work represents a significant advance on the problem of artifact verification, by considering a much richer and more realistic model than in previous work, incorporating core elements of IBM's successful Guard-Stage-Milestone model. In particular, the model features task hierarchy, concurrency, and richer artifact data. It also allows database key and foreign key dependencies, as well as arithmetic constraints. The results show decidability of verification and establish its complexity, making use of novel techniques including a hierarchy of Vector Addition Systems and a variant of quantifier elimination tailored to our context.