Restricciones de integridad referencial y dependencias de inclusión: claves para el enriquecimiento semántico de una base de datos

Una de las fuerzas que estimuló el desarrollo de la tecnología de bases de datos fue la necesidad de garantizar la consistencia de los datos almacenados. A medida que estos artefactos de software evolucionaron, se tendió a soportar un mayor contenido semántico de los datos, es decir que se incorporaron facilidades para representar objetos más complejos y mayor variedad de propiedades. Sin embargo, los DBMSs tradicionales proveen recursos limitados para expresarlas. Paralelamente, la adquisición de las propiedades de los datos a partir del Universo del Discurso (UdeD) se tornó también más compleja dando origen a novedosas áreas de desarrollo. Como consecuencia del enriquecimiento en la carga semántica de los datos surge la posibilidad de expresar variadas y valiosas conexiones entre los mismos. Por lo tanto, resulta imperativo contribuir en la identificación de las propiedades de los objetos del mundo real y sus relaciones con el objetivo de facilitar su representación fidedigna en el mundo de la base de datos, y fundamentalmente de constituir las bases de una documentación que permita su validación. Este proyecto tiene como objetivo el estudio de las relaciones como elementos que juegan un rol fundamental tanto en el UdeD como en el modelado, refinamiento y reingeniería de bases de datos.Eje: Bases de datosRed de Universidades con Carreras en Informática (RedUNCI

Restricciones de integridad referencial y dependencias de inclusión: claves para el enriquecimiento semántico de una base de datos

Una de las fuerzas que estimuló el desarrollo de la tecnología de bases de datos fue la necesidad de garantizar la consistencia de los datos almacenados. A medida que estos artefactos de software evolucionaron, se tendió a soportar un mayor contenido semántico de los datos, es decir que se incorporaron facilidades para representar objetos más complejos y mayor variedad de propiedades. Sin embargo, los DBMSs tradicionales proveen recursos limitados para expresarlas. Paralelamente, la adquisición de las propiedades de los datos a partir del Universo del Discurso (UdeD) se tornó también más compleja dando origen a novedosas áreas de desarrollo. Como consecuencia del enriquecimiento en la carga semántica de los datos surge la posibilidad de expresar variadas y valiosas conexiones entre los mismos. Por lo tanto, resulta imperativo contribuir en la identificación de las propiedades de los objetos del mundo real y sus relaciones con el objetivo de facilitar su representación fidedigna en el mundo de la base de datos, y fundamentalmente de constituir las bases de una documentación que permita su validación. Este proyecto tiene como objetivo el estudio de las relaciones como elementos que juegan un rol fundamental tanto en el UdeD como en el modelado, refinamiento y reingeniería de bases de datos.Eje: Bases de datosRed de Universidades con Carreras en Informática (RedUNCI

A Methodology for semantically enriching interoperable databases

Integrated access to a Federated Database System, requires a deep knowledge about the semantics of its component databases so that interdatabase semantic relationships can be detected. Unfortunately, very often there is a lack of such a knowledge and the local schemas do not help to acquire this knowledge. The solution is to upgrade the semantic level of the local schemas through a semantic enrichment process where implicit knowledge is discovered and made explicit. Here we outline a methodology for semantic enrichment consisting of two phases. In the knowledge acquisition phase, restrictions in the form of different types of identifiers and dependencies of several kinds are discovered by analyzing the intension and the extension of the database. Then, in the conversion phase, the schemas augmented with this knowledge are converted to rich schemas expressed in a canonical object oriented modelPostprint (published version

A Methodology for semantically enriching interoperable databases

Integrated access to a Federated Database System, requires a deep knowledge about the semantics of its component databases so that interdatabase semantic relationships can be detected. Unfortunately, very often there is a lack of such a knowledge and the local schemas do not help to acquire this knowledge. The solution is to upgrade the semantic level of the local schemas through a semantic enrichment process where implicit knowledge is discovered and made explicit. Here we outline a methodology for semantic enrichment consisting of two phases. In the knowledge acquisition phase, restrictions in the form of different types of identifiers and dependencies of several kinds are discovered by analyzing the intension and the extension of the database. Then, in the conversion phase, the schemas augmented with this knowledge are converted to rich schemas expressed in a canonical object oriented mode

Migrating relational databases into object-based and XML databases

Rapid changes in information technology, the emergence of object-based and WWW applications, and the interest of organisations in securing benefits from new technologies have made information systems re-engineering in general and database migration in particular an active research area. In order to improve the functionality and performance of existing systems, the re-engineering process requires identifying and understanding all of the components of such systems. An underlying database is one of the most important component of information systems. A considerable body of data is stored in relational databases (RDBs), yet they have limitations to support complex structures and user-defined data types provided by relatively recent databases such as object-based and XML databases. Instead of throwing away the large amount of data stored in RDBs, it is more appropriate to enrich and convert such data to be used by new systems. Most researchers into the migration of RDBs into object-based/XML databases have concentrated on schema translation, accessing and publishing RDB data using newer technology, while few have paid attention to the conversion of data, and the preservation of data semantics, e.g., inheritance and integrity constraints. In addition, existing work does not appear to provide a solution for more than one target database. Thus, research on the migration of RDBs is not fully developed. We propose a solution that offers automatic migration of an RDB as a source into the recent database technologies as targets based on available standards such as ODMG 3.0, SQL4 and XML Schema. A canonical data model (CDM) is proposed to bridge the semantic gap between an RDB and the target databases. The CDM preserves and enhances the metadata of existing RDBs to fit in with the essential characteristics of the target databases. The adoption of standards is essential for increased portability, flexibility and constraints preservation. This thesis contributes a solution for migrating RDBs into object-based and XML databases. The solution takes an existing RDB as input, enriches its metadata representation with the required explicit semantics, and constructs an enhanced relational schema representation (RSR). Based on the RSR, a CDM is generated which is enriched with the RDB's constraints and data semantics that may not have been explicitly expressed in the RDB metadata. The CDM so obtained facilitates both schema translation and data conversion. We design sets of rules for translating the CDM into each of the three target schemas, and provide algorithms for converting RDB data into the target formats based on the CDM. A prototype of the solution has been implemented, which generates the three target databases. Experimental study has been conducted to evaluate the prototype. The experimental results show that the target schemas resulting from the prototype and those generated by existing manual mapping techniques were comparable. We have also shown that the source and target databases were equivalent, and demonstrated that the solution, conceptually and practically, is feasible, efficient and correct

Migrating relational databases into object-based and XML databases

Rapid changes in information technology, the emergence of object-based and WWW applications, and the interest of organisations in securing benefits from new technologies have made information systems re-engineering in general and database migration in particular an active research area. In order to improve the functionality and performance of existing systems, the re-engineering process requires identifying and understanding all of the components of such systems. An underlying database is one of the most important component of information systems. A considerable body of data is stored in relational databases (RDBs), yet they have limitations to support complex structures and user-defined data types provided by relatively recent databases such as object-based and XML databases. Instead of throwing away the large amount of data stored in RDBs, it is more appropriate to enrich and convert such data to be used by new systems. Most researchers into the migration of RDBs into object-based/XML databases have concentrated on schema translation, accessing and publishing RDB data using newer technology, while few have paid attention to the conversion of data, and the preservation of data semantics, e.g., inheritance and integrity constraints. In addition, existing work does not appear to provide a solution for more than one target database. Thus, research on the migration of RDBs is not fully developed. We propose a solution that offers automatic migration of an RDB as a source into the recent database technologies as targets based on available standards such as ODMG 3.0, SQL4 and XML Schema. A canonical data model (CDM) is proposed to bridge the semantic gap between an RDB and the target databases. The CDM preserves and enhances the metadata of existing RDBs to fit in with the essential characteristics of the target databases. The adoption of standards is essential for increased portability, flexibility and constraints preservation. This thesis contributes a solution for migrating RDBs into object-based and XML databases. The solution takes an existing RDB as input, enriches its metadata representation with the required explicit semantics, and constructs an enhanced relational schema representation (RSR). Based on the RSR, a CDM is generated which is enriched with the RDB's constraints and data semantics that may not have been explicitly expressed in the RDB metadata. The CDM so obtained facilitates both schema translation and data conversion. We design sets of rules for translating the CDM into each of the three target schemas, and provide algorithms for converting RDB data into the target formats based on the CDM. A prototype of the solution has been implemented, which generates the three target databases. Experimental study has been conducted to evaluate the prototype. The experimental results show that the target schemas resulting from the prototype and those generated by existing manual mapping techniques were comparable. We have also shown that the source and target databases were equivalent, and demonstrated that the solution, conceptually and practically, is feasible, efficient and correct.EThOS - Electronic Theses Online ServiceGBUnited Kingdo