Objectives To provide methods and techniques for view-based query processing and for query optimization in the INFOMIX system. More precisely, different forms of query processing (query answering and query rewriting) and query optimization (static and dynamic) will be addressed.

Description of work TASK 1: Definition of query answering methods and techniques (Task Leader: UNIROME1). The problem of computing answers to queries expressed by the user against the global schema of the IIM will be addressed. In particular, techniques, methods and complexity of query answering in the INFOMIX framework will be investigated. TASK 2: Definition of query rewriting methods and techniques (Task Leader: UNIROME1). Techniques and methods for reformulating queries expressed by the user against the global schema of the IIM will be defined. While the previous task deals with the problem of accessing information sources for answering user queries, this task will address the problem of computing the perfect rewriting of the query: therefore, methods, techniques and complexity of query rewriting will be investigated. TASK 3: Definition of query optimization methods and techniques (Task Leader: TUWIEN). Query optimization are techniques highly important, because performance and scalability of a data integration approach to large amounts of data are two main criteria for its practical relevance. Query optimization can be effected both statically, by reasoning over queries and integrity constraints, and dynamically, combining query optimization with query execution. Concepts and techniques from query optimization in distributed databases need to be taken into account as well. Furthermore, the effectiveness of the optimization methods with respect to scalability needs to be assessed.

Deliverables D5.1- Methods and techniques for query answering (Report). This report presents and discusses techniques, algorithms and complexity of the query answering task for the INFOMIX data integration prototype to be built. D5.2- Methods and techniques for query rewriting (Report). This report presents and discusses techniques, algorithms and complexity of the query rewriting task for the INFOMIX data integration prototype to be built. D5.3- Methods and techniques for query optimization (Report). This report presents and discusses techniques and algorithms for optimizing the performance of the INFOMIX data integration prototype to be built, and assesses their effectiveness with respect to scalability.

Milestones and expected results M4 - Acceptance of the collection of algorithms for query reformulation and optimization. The workpackage provides detailed methods and techniques for computing the answer to user queries in the INFOMIX framework. Such a workpackage is therefore a central project step. Algorithms and techniques for query answering, query rewriting and query optimization for the INFOMIX data integration prototype to be built will be provided.