One of the great promises of Web service technology is re-use through composition of basic services into new virtual services. To facilitate easier development of such compositions, recent approaches to declarative service composition ask a composition designer to provide a declarative specification of a composition goal, instead of an imperative workflow of composed services. Middleware services use this goal and expressive descriptions of available services to automatically generate an imperative workflow. However, if an error occurs during this process the source of the problem becomes difficult to trace. In this paper, we discuss how an integration of two existing middleware infrastructures, the CSIRO's semantic composition architecture and the Web service offerings infrastructure (WSOl), can be used for monitoring of functional correctness and quality of service (QoS) in declarative Web service compositions. The combination supplements the generated workflows with checking of functional correctness, measurement and calculation of QoS metrics, and reporting of discovered problems. In future, it will be extended with correlation and analysis of monitored information to determine probable causes of problems and appropriate corrective actions. This will provide improved transparency and quality control that will be needed in practice.
['Kerry Taylor', 'Paul Brebner', 'Michael Kearney', 'Dana Zhang', 'Kelly Lam', 'Vladimir Tosic']
Towards Declarative Monitoring of Declarative Service Compositions