An Extension of an Algebra for Nested Relations
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چکیده
منابع مشابه
The Powerset Algebra as a Natural Tool to Handle Nested Database Relations
The nested relational algebra is often inadequate as a tool to handle nested relations, since several important queries, such as transitive closure, cannot expressed by it. On the other hand, the powerset algebra does allow the expression of transitive closure, but in a too expensive way. Therefore, we consider various other extensions to the nested algebra, such as least tixpoint and programmi...
متن کاملEquivalence and Normal Forms for the Restricted and Bounded Fixpoint in the Nested Algebra
The nested model is an extension of the traditional, \\at" relational model in which relations can also have relation-valued entries. Its \default" query language, the nested algebra, is rather weak, unfortunately, since it is only a conservative extension of the traditional, \\at" relational algebra, and thus can only express a small fraction of the polynomial-time queries. Therefore, it was p...
متن کاملThe Restricted and Bounded Fixpoint Closures of the Nested Relational Algebra are Equivalent
The nested model is an extension of the traditional, \ at" relational model in which relations can also have relation-valued entries. Its \default" query language, the nested algebra, is rather weak, unfortunately, since it is only a conservative extension of the traditional, \ at" relational algebra, and thus can only express a small fraction of the polynomial-time queries. Therefore, it was p...
متن کاملThe Restricted and Bounded Fixpoint Closures of the Nested Algebra are Equivalent
The nested model is an extension of the traditional, “flat” relational model in which relations can also have relationvalued entries. Its “default” query language, the nested algebra, is rather weak, unfortunately, since it is only a conservative extension of the traditional, “flat” relational algebra, and thus can only express a small fraction of the polynomial-time queries. Therefore, it was ...
متن کاملEquivalence of the Relational Algebra a N D Calculus for Nested Relations
Abstrac t -The relational model is extended to include nested structures. This extension is formalised using the distinction between a tuple scheme and a relation scheme. The algebra and calculus languages are defined for this model. It is shown that the restricted powerset is a derived operation in the algebra and the full powerset is expressible by a safe forraula in the calculus. Since the f...
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