how foreign function integration conquers heterogeneous query processing
With the emergence of application systems which encapsulate databases and related application components, pure data integration using, for example, a federated database system is not possible anymore. Instead, access via predefined functions is the only way to get data from an application system. As a result, retrieval of such heterogeneous and encapsulated data sources needs the combination of generic query as well as predefined function access. In this paper, we present a middleware approach supporting such a novel and extended kind of integration. Starting with the overall architecture, we explain the functionality and cooperation of its core components: a federated database system and a workflow management system connected via a wrapper. Afterwards, we concentrate on essential aspects of query processing across these heterogeneous components focusing on the impact of the functions included. We discuss the operations the wrapper should provide in order to extend the workflow system's native functionality. In addition to selection and projection, these operations could include aggregation and the support of subqueries. Moreover, we point out modifications to the traditional cost model needed to consider the cost estimates for the function calls as well.
function integration functional integrability heterogeneous query processing heterogeneity query processing query emergence applications systems data database component data integrity examples federated database system federated access retrieval combinational generic paper middleware support architecture cooperation operability core workflow management workflow management system workflow wrapper aspect order select project aggregate point cost model cost estimates