Algebraic Optimization of Relational Queries with Various Kinds of Preferences
Preferences can be used for information filtering and extraction to deliver the most relevant data to the user. Therefore the efficient integration of querying with preferences into standard database technology is an important issue. The paper resumes a logical framework for formulating preferences and their embedding into relational algebra through a single preference operator parameterized by a set of user preferences of sixteen various kinds and returning only the most preferred subsets of its argument relation. Most importantly, preferences between sets of elements can be expressed. To make a relational query language with the preference operator useful for practical applications, formal foundation for algebraic optimization, applying heuristics like push preference, has to be provided. Therefore abstract properties of the preference operator and a variety of algebraic laws describing its interaction with other relational algebra operators are presented.
Keywordslogic of preference relational query optimization
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