Publication: Extensiones de bases de datos relacionales y deductivas: fundamentos teóricos e implementación
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2016-06-30
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Universidad Complutense de Madrid
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Abstract
En esta memoria hacemos contribuciones dentro del campo de los lenguajes de bases de datos. Nos hemos propuesto tres objetivos fundamentales: 1. Mejorar la expresividad de los lenguajes de bases de datos actuales. 2. Desarrollar semánticas formales para nuestras propuestas de lenguajes de bases de datos extendidos. 3. Llevar a cabo la implementación de las semánticas anteriores en sistemas de bases de datos prácticos. Hemos conseguido estos tres objetivos en distintas áreas dentro de las bases de datos. Por un lado, en el campo de las bases de datos deductivas, proponemos HH:(C). Este lenguaje extiende las capacidades de los lenguajes de bases de datos deductivos con restricciones dado que permite consultas hipotéticas y cuanti cación universal. Por otro lado, utilizamos el estudio dentro de las bases de datos deductivas y lo aplicamos a las bases de datos relacionales. En concreto proponemos HR-SQL que incorpora consultas hipotéticas y de niciones recursivas no lineales y mutuamente recursivas. La idea tras esta propuesta es superar algunas limitaciones expresivas del lenguaje estándar de de nición de bases de datos SQL. A continuación introducimos ambas aproximaciones. Las fórmulas de Harrop hereditarias con restricciones, HH(C), se han usado como base para lenguajes de programación lógica con restricciones. Al igual que la programación lógica da soporte a lenguajes de bases de datos deductivas como Datalog (con restricciones), este marco se usa como base para un sistema de bases de datos deductivas que mejora la expresividad de los sistemas aparecidos hasta el momento. En el segundo capítulo de esta memoria se muestran los resultados teóricos que fundamentan el lenguaje HH:(C) y una implementación concreta de este esquema que demuestra la viabilidad y expresividad del esquema. Las principales aportaciones con respecto a Datalog son la incorporación de la implicación intuicionista, que permite formular hipótesis, y el uso de cuanti cadores incluso en el lenguaje de restricciones. El sistema está diseñado de forma que soporta diferentes sistemas de restricciones. La implementación incluye varios dominios concretos y también funciones de agregación y restricciones de integridad que son habituales en otros lenguajes de bases de datos relacionales. El signi cado del lenguaje se de ne mediante una semántica de pruebas y el mecanismo operacional se de ne mediante una sem ánica de punto jo que es correcta y completa con respecto a la primera. Para el cómputo de las consultas hipotéticas y de las funciones de agregación se hace uso de una noción de estrati cación más compleja que la que usa Datalog. La semántica de punto jo desarrollada constituye un marco apropiado que lleva a la implementación de un sistema concreto...
In this work we present some contributions to the eld of database languages. We consider three general goals: 1. Improve the expressiveness of current database languages. 2. Develop formal semantics for our proposal of extended database languages. 3. Implement these semantics into practical database systems. We have followed these steps moving in di erent database elds. On the one hand, in the deductive database eld, we have proposed HH:(C) which extends deductive database languages allowing hypothetical queries and universal quanti cations. On the other hand, we have moved to the relational database eld and proposed HR-SQL that incorporates hypothetical queries as well as recursive de nitions aimed to overcome some expressive limitations of standard database languages. Next, we introduce both proposals. The scheme of Hereditary Harrop formulas with constraints, HH(C), was proposed as a basis for Constraint Logic Programming languages. In the same way that Datalog emerges from logic programming as a deductive database language, such formulas can support a very expressive framework for constraint deductive databases, incorporating the intuitionistic implication that allows hypothetical queries and the use of quanti ers even in the constraint language. As negation is needed in the database eld, HH(C) is extended with negation to get HH:(C). The second chapter of this work presents the theoretical foundations of HH:(C) and an implementation that shows the viability and expressive power of the proposal. Moreover, the language is designed in a exible way in order to support di erent constraint systems. The implementation includes several domains, and it also supports aggregates and strong integrity constraints as found in database languages. The formal semantics of the language is de ned by a proof-theoretic calculus, and for the operational mechanism we use a strati ed xpoint semantics, which is proved to be sound and complete w.r.t. the former. Hypothetical queries and aggregates require a more involved strati cation than the common one used in Datalog. The resulting xpoint semantics constitutes a suitable foundation for the system implementation. The Structured Query Language (SQL) is one of the most recognized and used database languages. It can be considered as a declarative programming language, but in its origin it lacked recursion. Although nowadays there are SQL database systems that partially support recursion, current database systems supporting recursive SQL impose restrictions on queries such as linearity, and do not allow mutual recursion. In addition, those systems are not founded on a formal semantics...
In this work we present some contributions to the eld of database languages. We consider three general goals: 1. Improve the expressiveness of current database languages. 2. Develop formal semantics for our proposal of extended database languages. 3. Implement these semantics into practical database systems. We have followed these steps moving in di erent database elds. On the one hand, in the deductive database eld, we have proposed HH:(C) which extends deductive database languages allowing hypothetical queries and universal quanti cations. On the other hand, we have moved to the relational database eld and proposed HR-SQL that incorporates hypothetical queries as well as recursive de nitions aimed to overcome some expressive limitations of standard database languages. Next, we introduce both proposals. The scheme of Hereditary Harrop formulas with constraints, HH(C), was proposed as a basis for Constraint Logic Programming languages. In the same way that Datalog emerges from logic programming as a deductive database language, such formulas can support a very expressive framework for constraint deductive databases, incorporating the intuitionistic implication that allows hypothetical queries and the use of quanti ers even in the constraint language. As negation is needed in the database eld, HH(C) is extended with negation to get HH:(C). The second chapter of this work presents the theoretical foundations of HH:(C) and an implementation that shows the viability and expressive power of the proposal. Moreover, the language is designed in a exible way in order to support di erent constraint systems. The implementation includes several domains, and it also supports aggregates and strong integrity constraints as found in database languages. The formal semantics of the language is de ned by a proof-theoretic calculus, and for the operational mechanism we use a strati ed xpoint semantics, which is proved to be sound and complete w.r.t. the former. Hypothetical queries and aggregates require a more involved strati cation than the common one used in Datalog. The resulting xpoint semantics constitutes a suitable foundation for the system implementation. The Structured Query Language (SQL) is one of the most recognized and used database languages. It can be considered as a declarative programming language, but in its origin it lacked recursion. Although nowadays there are SQL database systems that partially support recursion, current database systems supporting recursive SQL impose restrictions on queries such as linearity, and do not allow mutual recursion. In addition, those systems are not founded on a formal semantics...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Sistemas Informáticos y Computación, leída el 16-12-2015