Process Query Language : Design , Implementation and Evaluation

Organisations can derive significant benefits from the use of practices, techniques, and tools from the area of business process management. Through the concomitant focus on processes they may acquire a substantial number of process models and such large collections of models require management, including support for versioning, merging, conformance checking, and retrieval. Model retrieval thus far has mostly focussed on querying models using syntactic properties of their control flow rather than on exploiting semantic properties capturing aspects of model execution. While the latter is (much) more challenging, it is also more effective, especially in a context where process models serve as a basis for subsequent automation. The focus of this paper is to overcome the challenges associated with semantic querying of process model collections and thus unlocking its benefits. The first challenge concerns determining decidability of the building blocks of the semantic query language, i.e. semantic relations between tasks. This is important as not all such relations can necessarily be computed, especially if one allows them to be based on unrestricted temporal logic statements. The second challenge concerns useability, specifically, selecting those semantic relations among those that are computable that are also considered relevant and intuitive by domain experts. The third and final challenge is concerned with achieving acceptable performance of query evaluation. The evaluation of a query may require expensive checks on all process models (of which there may be thousands) and to deal with this suitable index structures should be put in place. The effectiveness of these structures should be demonstrated empirically.