Artifact-Centric Workflow Dominance

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Abstract

In this paper we initiate a study on comparing artifact-centric workflow schemas, in terms of the ability of one schema to emulate the possible behaviors of another schema. Artifact-centric workflows are centered around “business artifacts”, which contain both a data schema, which can hold all of the data about a key business entity as it passes through a workflow, along with a lifecycle schema, which specifies the possible ways that the entity can evolve through the workflow. In this paper, the data schemas for artifact types are finite sets of attribute-value pairs, and the lifecycle schemas are specified as sets of condition-action rules, where the condition is evaluated against the current snapshot of the artifact, and where the actions are external services (or “tasks”), which read a subset of the attributes of an artifact, which write onto a subset of the attributes, and which are performed by an entity outside of the workflow system (often a human). The services are also characterized by pre- and post-conditions, in the spirit of semantic web services. To compare artifact-centric workflows, we introduce the notion of “dominance”, which intuitively captures the fact that all executions of a workflow can be emulated by a second workflow. (In the current paper, the emulation is focused only on the starting and ending snapshots of the possible enactments of the two workflows.) In fact, dominance is a parametric notion that depends on the characterization of the policies that govern the execution of the services invoked by the workflows. In this paper, we study in detail the case of “absolute dominance”, in which this policy places no constraints on the possible service executions. We provide decidability and complexity results for bounded and unbounded workflow executions in the cases where the values in an artifact range over an infinite structure, such as the integers, the rationals, or the reals, possibly with order, addition, or multiplication.