Federated database systems for managing distributed, heterogeneous, and autonomous databases
ACM Computing Surveys (CSUR) - Special issue on heterogeneous databases
Query processing in multidatabase systems
Modern database systems
Query optimization in the presence of limited access patterns
SIGMOD '99 Proceedings of the 1999 ACM SIGMOD international conference on Management of data
Production workflow: concepts and techniques
Production workflow: concepts and techniques
Access path selection in a relational database management system
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
An Approach to Schema Integration and Query Formulation in Federated Database Systems
Proceedings of the Third International Conference on Data Engineering
Object Exchange Across Heterogeneous Information Sources
ICDE '95 Proceedings of the Eleventh International Conference on Data Engineering
Don't Scrap It, Wrap It! A Wrapper Architecture for Legacy Data Sources
VLDB '97 Proceedings of the 23rd International Conference on Very Large Data Bases
Query Optimization in the Presence of Foreign Functions
VLDB '93 Proceedings of the 19th International Conference on Very Large Data Bases
Querying Heterogeneous Information Sources Using Source Descriptions
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
The intrinsic problems of structural heterogeneity and an approach to their solution
The VLDB Journal — The International Journal on Very Large Data Bases
Capability-Sensitive Query Processing on Internet Sources
ICDE '99 Proceedings of the 15th International Conference on Data Engineering
WISE '00 Proceedings of the First International Conference on Web Information Systems Engineering (WISE'00)-Volume 1 - Volume 1
EDBT '02 Proceedings of the 8th International Conference on Extending Database Technology: Advances in Database Technology
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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.