Data-centric Web Services Based on Business Artifacts

Existing Web services standards consider data primarily on the level of inputs and outputs specifications, with the major focus on functional aspects of interactions. Majority of applications rely on data sources, but such data sources are not part of the Web service specifications and cannot be accessed directly by clients. The fact that data are treated independently or as second-class citizens severely limits re-use, flexibility, customization and integration options of current Web services. In this paper we suggest to extend the WS specifications by introducing a data-centric Web services model that integrates functional and data perspectives in one coherent framework. The approach is based on Business Artifacts and in particular on the declarative modular Guard-Stage-Milestone (GSM) model. We introduce a Web Data- and Artifact- centric Service (W-DAS) model using GSM in its core which in addition to usual application specific WS operations defines a set of data access interfaces including CRUD operations, artifacts retrieval interface for querying, filtering and sorting data, and operations for arbitrary custom defined ad hoc run-time queries. We discuss W-DAS publish-subscribe mechanisms and implementation.