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As an expressive knowledge representation language for Semantic Web, Web Ontology Language (OWL) plays an important role in areas like science and commerce. The problem of maintaining integrity constraints arises because OWL employs the Open World Assumption (OWA) as well as the Non-Unique Name Assumption (NUNA). These assumptions are typically suitable for representing knowledge distributed across the Web, where the complete knowledge about a domain cannot be assumed, but make it challenging to use OWL itself for closed world integrity constraint validation. Integrity constraints (ICs) on ontologies have to be enforced; otherwise conflicting results would be derivable from the same knowledge base (KB). The current trends of incorporating ICs into OWL are based on its query language SPARQL, alternative semantics, or logic programming. These methods usually suffer from limited types of constraints they can handle, and/or inherited computational expensiveness. This dissertation presents a comprehensive and efficient approach to maintaining integrity constraints. The design enforces data consistency throughout the OWL life cycle, including the processes of OWL generation, maintenance, and interactions with other ontologies. For OWL generation, the Paraconsistent model is used to maintain integrity constraints during the relational database to OWL translation process. Then a new rule-based language with set extension is introduced as a platform to allow users to specify constraints, along with a demonstration of 18 commonly used constraints written in this language. In addition, a new constraint maintenance system, called Jena2Drools, is proposed and implemented, to show its effectiveness and efficiency. To further handle inconsistencies among multiple distributed ontologies, this work constructs a framework to break down global constraints into several sub-constraints for efficient parallel validation.

Integrity constraints comprise an urgent part of conceptual models. For this reason, they must be structured and represented in orderly manner. The purpose of this work is to solve the problems inherent in creation, storage and retrieval of centralized data integrity constraints. This paper analyses the methods for implementation of data integrity constraints and describes a Oracle RDBMS-based technique that enables for impeccable functionality of information system and protection from invalid data. After analysis of system requirements and currently available software solutions, UML models of system architecture, data and database were proposed. Suitable means were chosen for developing a system for centralist management of data integrity constraints. The Constraint Editor geared towards designing, implementing and maintaining of procedures, integrity constraints throughout their lifecycle was developed. A simple, functional and intuitive graphical user interface makes data integrity constraints easy to story, manage and retrieve. The created software makes optimal use of RDBVS resources while performing ETL processes with multi – table insertions. The ability to insert data into multiple tables ensures further possibilities of supplying standard statistical analysis software with correct data and better performance than a procedure to perform multiple insertions using "IF..THEN" syntax. Furthermore, the software verifies SQL DML functions system widethus protecting... [to full text]

O fator temporal é uma variável natural da maioria dos sistemas de informação, pois no mundo real os eventos ocorrem de maneira dinâmica, modicando continuamente os valores dos seus objetos no decorrer do tempo. Muitos desses sistemas precisam registrar essa modicação e atribuir os instantes de tempo em que cada informação foi válida no sistema. Este trabalho reúne as características relacionadas aos Bancos de Dados Temporais e Bancos de Dados Objeto-Relacionais. O objetivo primordial é propor uma forma de implementar alguns aspectos temporais, desenvolvendo um módulo que faça parte das características e funcionalidades internas de um SGBD. O módulo temporal contempla principalmente a parte de restrições de integridade temporal que é utilizada para manter a consistência da informação temporal armazenada. Para isso, é proposto um novo tipo de dado que melhor representa as marcas temporais dos objetos. Uma parte importante para a implementação desse projeto é a utilização de um SGBD objeto-relacional que possui algumas características orientadas a objetos que permitem a extensão de seus recursos, tornando-o capaz de gerenciar alguns aspectos temporais. O módulo temporal desenvolvido torna esses aspectos temporais transparentes para o usuário. Por conseqüência, esses usuários são capazes de utilizar os recursos temporais com maior naturalidade. / The temporal factor is a natural variable of the majority of the information systems, therefore in the real world the events occur in dynamic way, modifying continuously the values of its objects in elapsing of the time. Many of these systems need to register this modication and to attribute the instants of time where each information was valid in the system. This work congregates the characteristics related to the Temporal Databases and Object-Relational Databases. The primordial objective is to consider a form to implement some temporal aspects, developing a module that is part of the characteristics and internal functionalities of a DBMS. The temporal module mainly contemplates the part of restrictions of temporal integrity that is used to keep the consistency of the stored temporal information. For this, a new data type is proposed that better represent the objects timestamps. An important part for the implementation of this project is the use of a object-relational DBMS that has some object-oriented characteristics that allow the extension of its resources, becoming capable to manage some temporal aspects. The developed temporal module becomes these transparent temporal aspects for the user. For consequence, these users are capable to use the temporal resources more naturally.

<p>The software industry is facing a great challenge. While systems get more complex and distributed across the world, users are becoming more dependent on their availability. As systems increase in size and complexity so does the risk that some part will fail. Unfortunately, it has proven hard to tackle faults in distributed systems without a rigorous approach. Therefore, it is crucial that the scientific community can provide answers to how distributed computer systems can continue functioning despite faults.</p><p>Our contribution in this thesis is regarding a special class of faults which occurs whennetwork links fail in such a way that parts of the network become isolated, such faults are termed network partitions. We consider the problem of how systems that have integrity constraints on data can continue operating in presence of a network partition. Such a system must act optimistically while the network is split and then perform a some kind of reconciliation to restore consistency afterwards.</p><p>We have formally described four reconciliation algorithms and proven them correct. The novelty of these algorithms lies in the fact that they can restore consistency after network partitions in a system with integrity constraints and that one of the protocols allows the system to provide service during the reconciliation. We have implemented and evaluated the algorithms using simulation and as part of a partition-tolerant CORBA middleware. The results indicate that it pays off to act optimistically and that it is worthwhile to provide service during reconciliation.</p>

In today’s emerging information systems, it is natural to have data distributed across multiple sites. We define a System of Databases (SyDb) as a collection of autonomous and heterogeneous databases. R-SyDb (System of Relational Databases) is a restricted form of SyDb, referring to a collection of relational databases, which are independent. Similarly, X-SyDb (System of XML Databases) refers to a collection of XML databases. Global integrity constraints ensure integrity and consistency of data spanning multiple databases. In this dissertation, we present (i) Constraint Checker, a general framework of a mobile agent based approach for checking global constraints on R-SyDb, and (ii) XConstraint Checker, a general framework for checking global XML constraints on X-SyDb. Furthermore, we formalize multiple efficient algorithms for varying semantic integrity constraints involving both arithmetic and aggregate predicates. The algorithms take as input an update statement, list of all global semantic integrity constraints with arithmetic predicates or aggregate predicates and outputs sub-constraints to be executed on remote sites. The algorithms are efficient since (i) constraint check is carried out at compile time, i.e. before executing update statement; hence we save time and resources by avoiding rollbacks, and (ii) the implementation exploits parallelism. We have also implemented a prototype of systems and algorithms for both R-SyDb and X-SyDb. We also present performance evaluations of the system.

O fator temporal é uma variável natural da maioria dos sistemas de informação, pois no mundo real os eventos ocorrem de maneira dinâmica, modicando continuamente os valores dos seus objetos no decorrer do tempo. Muitos desses sistemas precisam registrar essa modicação e atribuir os instantes de tempo em que cada informação foi válida no sistema. Este trabalho reúne as características relacionadas aos Bancos de Dados Temporais e Bancos de Dados Objeto-Relacionais. O objetivo primordial é propor uma forma de implementar alguns aspectos temporais, desenvolvendo um módulo que faça parte das características e funcionalidades internas de um SGBD. O módulo temporal contempla principalmente a parte de restrições de integridade temporal que é utilizada para manter a consistência da informação temporal armazenada. Para isso, é proposto um novo tipo de dado que melhor representa as marcas temporais dos objetos. Uma parte importante para a implementação desse projeto é a utilização de um SGBD objeto-relacional que possui algumas características orientadas a objetos que permitem a extensão de seus recursos, tornando-o capaz de gerenciar alguns aspectos temporais. O módulo temporal desenvolvido torna esses aspectos temporais transparentes para o usuário. Por conseqüência, esses usuários são capazes de utilizar os recursos temporais com maior naturalidade. / The temporal factor is a natural variable of the majority of the information systems, therefore in the real world the events occur in dynamic way, modifying continuously the values of its objects in elapsing of the time. Many of these systems need to register this modication and to attribute the instants of time where each information was valid in the system. This work congregates the characteristics related to the Temporal Databases and Object-Relational Databases. The primordial objective is to consider a form to implement some temporal aspects, developing a module that is part of the characteristics and internal functionalities of a DBMS. The temporal module mainly contemplates the part of restrictions of temporal integrity that is used to keep the consistency of the stored temporal information. For this, a new data type is proposed that better represent the objects timestamps. An important part for the implementation of this project is the use of a object-relational DBMS that has some object-oriented characteristics that allow the extension of its resources, becoming capable to manage some temporal aspects. The developed temporal module becomes these transparent temporal aspects for the user. For consequence, these users are capable to use the temporal resources more naturally.

The most important integrity constraints in XML are primary keys and foreign keys. In general, keys are essential in understanding both the structure and properties of data. They provide an instrument by which va- lues from a given set of attributes uniquely identify tuples in a database. As a result, keys are important to main database operations. Since XML beco- mes lingua franca for data exchange on the web, it is widely accepted as a model of real world data. Because XML documents in general can appear in any semi-structured form, structural constraints (including keys) are often imposed on the data that are to be modified or processed These constra- ints are formally defined in a schema.Unfortunately, in spite of the obvious advantages, the presence of a schema is not mandatory and many XML do- cuments are not joined with any. Consequently, no integrity constratins are specified in those documents, neither. This thesis is mainly focused on the inference of primary and foreign keys from XML documents. 1

The software industry is facing a great challenge. While systems get more complex and distributed across the world, users are becoming more dependent on their availability. As systems increase in size and complexity so does the risk that some part will fail. Unfortunately, it has proven hard to tackle faults in distributed systems without a rigorous approach. Therefore, it is crucial that the scientific community can provide answers to how distributed computer systems can continue functioning despite faults. Our contribution in this thesis is regarding a special class of faults which occurs whennetwork links fail in such a way that parts of the network become isolated, such faults are termed network partitions. We consider the problem of how systems that have integrity constraints on data can continue operating in presence of a network partition. Such a system must act optimistically while the network is split and then perform a some kind of reconciliation to restore consistency afterwards. We have formally described four reconciliation algorithms and proven them correct. The novelty of these algorithms lies in the fact that they can restore consistency after network partitions in a system with integrity constraints and that one of the protocols allows the system to provide service during the reconciliation. We have implemented and evaluated the algorithms using simulation and as part of a partition-tolerant CORBA middleware. The results indicate that it pays off to act optimistically and that it is worthwhile to provide service during reconciliation.