Querying an Integrated Complex-Object Dataflow Database.

We consider an integrated complex-object dataflow database in which multiple dataflow specifications can be stored, together with multiple executions of these dataflows, including the complex-object data that are involved, and annotations. We focus on dataflow applications frequently encountered in the scientific community, involving the manipulation of data with a complex-object structure combined with service calls, which can be either internal or external. Internal services are dataflows acting as a subprogram of an other dataflow, whereas external services are modeled as functions with a possibly non-deterministic behavior. Dataflow specifications are expressed in a high-level programming language based on the nested relational calculus, the operators of which provide the right “glue” needed to combine different service calls into a complex-object dataflow. All entities involved, whether complex-objects, dataflow executions or dataflow specifications, are first-class citizens of the integrated database: they are all data. We discuss how such dataflow repositories can be queried in a variety of ways, including provenance queries. We show that a modern SQL platform with support for (external) routines and SQL/XML suffices to support all types of dataflow repository queries.