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An object-oriented data and query model

Vella, Joseph (2013) An object-oriented data and query model. PhD thesis, University of Sheffield.

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Abstract

OODBs build effective databases with their development peaking in 2000. A reason given for its neglect is of not having a declarative and procedural language. Relevant declarative languages include ODMG OQL and Flora-2, a first order and object-oriented logic programming system based on F-Logic. Few procedural object algebras have been proposed and ours is one and none are offered together. The characteristics of the algebra proposed and implemented with Flora-2 are: it is closed; it is typed; its ranges and outputs are homogeneous sets of objects; operators work on either values or logical identifiers; a result set is asserted; and a query expression’s meta details are asserted too. The algebra has ten operators and most have algebraic properties. A framework was developed too and it has its object base loaded with methods that maintain it and our algebra. A framework’s function is to read an EERM diagram to assert the respective classes and referential constraints. The framework then sifts for nonimplementable constructs in the EERM diagram and converts them into implementable ones (e.g. n-ary relationships) and translate the object base design into ODMG ODLs. This translation’s correctness and completeness is studied. The framework implements run-time type checking as Flora-2 lacks these. We develop type checking for methods that are static, with single arity, polymorphic (e.g. overloaded and bounded), and recursive structures (e.g. lists) through well-known and accepted techniques. A procedure that converts a subset of OQL into an algebraic expression is given. Once created it is manipulated to produce an optimised expression through a number of query rewriting methods: e.g. semantic, join reduction, and view materialisation. These techniques are aided by the underlying object base constructs; e.g. primary key constraint presence is used to avoid duplicate elimination of a result set. We show the importance of tight coupling in each translation step from an EERM to an algebraic expression. Also we identify invariant constructs, e.g. primary key through a select operand, which do not change from a query range to a query result set.

Item Type: Thesis (PhD)
Keywords: database data model, database query model, object-oriented databases
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Computer Science (Sheffield)
The University of Sheffield > Faculty of Science (Sheffield) > Computer Science (Sheffield)
Identification Number/EthosID: uk.bl.ethos.589269
Depositing User: Mr Joseph Vella
Date Deposited: 13 Jan 2014 14:56
Last Modified: 03 Oct 2016 11:03
URI: http://etheses.whiterose.ac.uk/id/eprint/4914

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