A Flexible Directory Query Language for the Efficient Processing of Service Composition Queries

Service composition is a major challenge in an open environment populated by large numbers of heterogeneous services. In such a setting, the efficient interaction of directory-based service discovery with service composition engines is crucial. In this article we present a Java-based directory that offers special functionality enabling effective service composition. In order to optimize the interaction of the directory with different service composition algorithms exploiting application-specific heuristics, the directory supports user-defined selection and ranking functions written in a declarative query language. Inside the directory queries are transformed and compiled to JVM bytecode which is dynamically linked into the directory. The compiled query enables a best-first search of matching directory entries, efficiently pruning the search space.