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Safety, domain independence and translation of complex value database queries |
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| Authors: | Hong-Cheu Liu Jeffrey Xu Yu |
| Affiliation: | a Department of Computer Science and Information Engineering, Diwan University, Tainan County 72153, Taiwan b Department of Systems Engineering and Engineering Management, The Chinese University of Hong Kong, Hong Kong, China c Department of Computer Science, The Australian National University, Canberra ACT 0200, Australia |
| Abstract: | This paper considers the theory of database queries on the complex value data model with external functions. Motivated by concerns regarding query evaluation, we first identify recursive sets of formulas, called embedded allowed, which is a class with desirable properties of “reasonable” queries.We then show that all embedded allowed calculus (or fix-point) queries are domain independent and continuous. An algorithm for translating embedded allowed queries into equivalent algebraic expressions as a basis for evaluating safe queries in all calculus-based query classes has been developed.Finally we discuss the topic of “domain independent query programs”, compare the expressive power of the various complex value query languages and their embedded allowed versions, and discuss the relationship between safety, embedded allowed, and domain independence in the various calculus-based queries. |
| Keywords: | Complex value Safe query Domain independence Query translation Expressive power |
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