Policy-Driven Middleware for Manageable and Adaptive Web Services Compositions

MASC (Manageable and Adaptive Service Compositions)1 is a policy-based middleware for monitoring of Web service compositions and their dynamic adaptation to various runtime changes. The monitorable requirements and the adaptation actions are specified in the WS-Policy4MASC language which extends WS-Policy by defining new types of policy assertions. In this paper, we present an overview of MASC architecture and implementation. Compared with recent related works, MASC has several distinctive characteristics: (1) support for synchronous and asynchronous monitoring and coordination of adaptation both at the SOAP messaging layer and the process orchestration layer, (2) greater diversity of monitoring and control constructs, for example, a sub-process (or an activity) can be added, removed, replaced, skipped, or retried, (3) the externalization of monitoring and adaptation actions from definitions of business processes, (4) use of both technical and business metrics for adaptation decisions, and (5) extend the power and flexibility of the new Microsoft .NET 3.0 platform. We have implemented a MASC proof-of-concept prototype and evaluated it on monitoring and adaptation scenarios from a stock trading case study.