Orc-X: Combining Orchestrations and XQuery

In designing a language for distributed computing, the handling of data and distribution can be viewed as largely orthogonal concerns, as long as the data model supports the communication requirements of the distribution model. This view contrasts strongly with approaches based on distributed objects, which typically enforce a tight coupling of state and behavior. We have previously presented Orc, a language that provides simple but powerful constructs to orchestrate distributed computations. Previous versions of Orc included only simple data types, since these were sufficient to demonstrate the concurrency primitives. However, Orc’s communication model is based on web services, which support complex XML documents in addition to simple data types. Thus it is natural to consider XML as an appropriate data model for Orc. We present Orc-X, an extension of the Orc language with an XML data model and XML-specific data management capabilities from XQuery. We demonstrate that Orc-X is well-suited for the application domain of distributed resource management protocols such as the Narada mesh overlay protocol.