publication . Doctoral thesis . 2007

Rewriting Declarative Query Languages

Brantner, Matthias;
Open Access German
  • Published: 01 Jan 2007
  • Publisher: Universität Mannheim
  • Country: Germany
Abstract
Queries against databases are formulated in declarative languages. Examples are the relational query language SQL and XPath or XQuery for querying data stored in XML. Using a declarative query language, the querist does not need to know about or decide on anything about the actual strategy a system uses to answer the query. Instead, the system can freely choose among the algorithms it employs to answer a query. Predominantly, query processing in the relational context is accomplished using a relational algebra. To this end, the query is translated into a logical algebra. The algebra consists of logical operators which facilitate the application of various optimi...
Subjects
ACM Computing Classification System: InformationSystems_DATABASEMANAGEMENT
free text keywords: 004 Informatik
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58 references, page 1 of 4

7.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

7.1.1 Algebraic XPath Evaluation . . . . . . . . . . . . . . . . . 133

7.1.2 Unnesting XPath Expressions . . . . . . . . . . . . . . . . 133

7.1.3 Disjunctive Unnesting for XPath . . . . . . . . . . . . . . . 134

7.1.4 Disjunctive Unnesting for SQL . . . . . . . . . . . . . . . . 135

7.1.5 Preparing XQuery for Plan Generation . . . . . . . . . . . . 135

7.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

7.2.1 XML Query Processing . . . . . . . . . . . . . . . . . . . 136

7.2.2 Unnesting Disjunctive SQL Queries . . . . . . . . . . . . . 137 A Proofs for Unnesting XPath Queries 139

A.1 Proof of Equivalence 3.1 . . . . . . . . . . . . . . . . . . . . . . . 139

A.2 Proof of Equivalence 3.2 . . . . . . . . . . . . . . . . . . . . . . . 141

A.3 Proof of Equivalence 3.3 . . . . . . . . . . . . . . . . . . . . . . . 142

A.4 Proof of Equivalence 3.4 . . . . . . . . . . . . . . . . . . . . . . . 143

A.5 Proof of Equivalence 3.5 . . . . . . . . . . . . . . . . . . . . . . . 144

A.6 Proof of Equivalence 3.6 . . . . . . . . . . . . . . . . . . . . . . . 146

58 references, page 1 of 4
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