Database method schemas: A model for object based and parallel database computation
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| Publicado en: | ProQuest Dissertations and Theses (1996) |
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ProQuest Dissertations & Theses
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| Acceso en línea: | Citation/Abstract Full Text - PDF |
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| Resumen: | A model capturing the data manipulation capabilities of a large class of deterministic methods in object-oriented databases is proposed and investigated. The model uses a parallel synchronous semantics with concurrent-read and concurrent-write. Many results focus on the expressive power of methods and help understand various constructs and semantics associated with methods. A language independent notion of expressive completeness is given that, unlike previous notions, admits both object creation and database updates. Database Method Schemas are shown to express essentially the same transformations as a powerful declarative database language $(Datalog\sbsp{\infty}{\neg*}).$ Moreover, the transformations expressible in Database Method Schemas and $Datalog\sbsp{\infty}{\neg*}$ are algebraically characterized by relating the automorphism groups of inputs and outputs. Restrictions of methods providing various tractability guarantees are also discussed. The restrictions correspond closely to well-known relational query languages such as relational calculus, Datalog, the fixpoint queries, and the while queries. Database Method Schemas is a model of database parallel computation which makes explicit the potential parallelism in databases. The impact of new language constructs on expressiveness with respect to object creation is investigated and constructs based on expanded notions of deep equality are introduced to increase expressive power. In particular, a tractable construct yielding a language complete with respect to object creation is given for the first time. The new construct is also relevant to query complexity; for example, it allows expressing in polynomial time some queries, like counting, requiring exponential space in Database Method Schemas alone. |
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| ISBN: | 9798691278754 |
| Fuente: | ProQuest Dissertations & Theses Global |