Minimization of tree pattern queries
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
Preference formulas in relational queries
ACM Transactions on Database Systems (TODS)
Foundations of preferences in database systems
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
Order-preserving optimization of twig queries with structural preferences
IDEAS '08 Proceedings of the 2008 international symposium on Database engineering & applications
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Today user-centered information acquisition over collections of complex XML documents is increasingly in demand. To this end, preferences have become an important paradigm enabling users to express individual interests and delivering personalized information. As the structure of XML documents plays a major part in retrieval, users often have specific preferences about the structure. For evaluation a query has to be unfolded into an entire set of queries filling the structure with more or less preferred values. Since such structure expansions typically contain redundancies, it is important to identify and simplify necessary expansion queries for effective evaluation. To address these issues, we developed a preference query optimizer that not only determines an optimal set of expansion queries, but also preserves the specific ordering induced by the user preferences with respect to Pareto optimality.