Query Rewriting in the Presence of Functional Dependencies with Lossless Join Decomposition
qbai qbai, Jun Sik Hong, MF McTear · Information Integration and Web-based Applications & Services · 2003
Query rewriting is an essential issue in data integration systems over the Web and has received considerable attention. Many rewriting algorithms, e.g., the bucket algorithm, the inverse rules algorithm, the SVB algorithm and the MiniCon algorithm, have been proposed to address this issue in the absence of functional dependencies. These algorithms can be divided into two categories: bucket-based algorithms and inverse rule-based algorithms. All the bucket-based algorithms may sometimes miss query rewritings in the presence of functional dependencies with/without lossless join decomposition because they do not consider the effects of functional dependencies. However, some efforts have been made in developing inverse rule-based algorithms to solve this problem. In this paper, we propose an algorithm for query rewriting using views in the presence of functional dependencies with lossless join decomposition, which solves the problem of missing query rewritings in the MiniCon algorithm. We analyse the violation situation of the unification process in the MiniCon algorithm and describe our approach to handling such violation. Our algorithm extends the MiniCon algorithm to cope with query rewriting using views in the presence of functional dependencies with lossless join decomposition.