Artifact-centric design principle promotes business artifacts to the central role. Services in an artifact system are operations that change the state of these artifacts. A business rule specifies a condition to invoke a service, and a set of rules form a business process. Analogous to the service composition problem in Service Oriented Architecture, one can synthesize an artifact-centric process automatically from a given set of artifacts and services. However, handling uncontrollable events such as user behavior and conditional effects is a challenge. With a few exceptions that target at specific models, existing composition algorithms either assume deterministic outcome of uncontrollable events, or use the execution monitoring and replanning technique. Replanning may be late and miss the opportunity to achieve the goal. In this paper, we introduce a branch of control theory, called Discrete Event Systems (DES) theory, for process synthesis. This theory applies discrete state space models such as automata and Petri nets. The objective is to synthesize the control logic that achieves a given specification. With automaton model, the control logic is represented by state-action pairs that closely resemble rules in artifact systems. While planning techniques are usually optimistic in the sense that they search for the optimal path to achieve the goal, DES theory considers all possible paths and tries to guarantee the specification under the worst sequence of uncontrollable events. We use Google Checkout Service to illustrate our process synthesis technique.
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