A Formal Introduction to Business Artifacts with Guard-Stage-Milestone Lifecycles

A promising approach to managing business operations is based on business artifacts(a.k.a. business entities with lifecycles). These are key conceptual entities that are central to guid ing the operations of a business, and whose content changes as they move through those operations. An artifact type includes both an information modelthat captures, in either materialized or virtual form, all o f the business-relevant data about entities of that type, and a lifecycle model, that specifies the possible ways an entity of that type might progress through the business by responding to events and invoking services, including human activities. While most previous work on artifacts has focused on the use of lifecycle models based on variants of finite state machines, two recent papers have i ntroduced and studied the Guard-StageMilestone (GSM) meta-model for artifact lifecycles. GSM lifecycles are su bstantially more declarative than the finite state machine variants, and support hierarch y and parallelism within a single artifact instance. This report presents in detail the formal operational semantics of GSM. This report is intended to serve as the authoritative source on the semantics of GSM; implementation efforts such as the Barcelona prototype engine may use this document as a reference manual. The flow of activity, and interactions between artifact instances, are supported both throu gh testing of conditions against the artifact instances, and through events coming from an external environment or resulting from changes in artifact instances. The core of the operational semantics is based on the use of rules that are inspired by the Event-Condition-Action (ECA) rules paradigm. A key result here shows the equivalence of three different formulations of the GSM operational semantics. One formulation is based on incremental application