Doctoral Thesis / Dissertation from the year 2006 in the subject Computer Science - Applied, grade: 1.0, University of Dusseldorf "Heinrich Heine", language: English, abstract: Federated information systems provide access to interrelated data that is distributed over multiple autonomous and heterogeneous data sources. The integration of these sources demands for flexible and extensible architectures that balance both, the highest possible autonomy and a reasonable degree of information sharing. In current federated information systems, the integrated data sources do only have passive functionality with regard to the federation. However, continuous improvements take the functionality of modern databases beyond former limits. The significant improvement, on which this work is based on, is the ability of modern active database systems to execute programs written in a standalone programming language as user-defined functions or stored procedures from within their database management systems. We introduce Enhanced Active Database Systems as a new subclass of active databases that are able to interact with other components of a federation using external program calls from within triggers. We present several concepts and architectures that are specifically developed for Enhanced Active Databases to improve interoperability and consistency in federated information systems. As the basic concept we describe Active Event Notifications to provide an information system with synchronous and asynchronous update notifications in real-time. Based on this functionality, Enhanced Active Databases are able to actively participate in global integrity maintenance executing partial constraint checks on interrelated remote data. Furthermore, we present an architecture for a universal wrapper component that especially supports Active Event Notifications, which makes it perfectly suitable for event-based federated systems with real-time data processing. This tightly coupled wrapper archite

The emerging application-to-application paradigm allows an organization's data to be shared across applications in both intra-enterprise and inter-enterprise contexts. In order to seamlessly integrate information from disparate, heterogeneous, and multi-organizational applications and quickly adapt to new application contexts, rigid information modeling and proprietary data representation technology have proven inadequate. Conventional data integration approaches are based on database systems that represent data semantics using static structured data schemas. They cannot provide adequate facilities to satisfy the increasing need for effective and efficient application data integration from heterogeneous data sources. Applications need to be built on an information model that is standards-based, flexible, and adaptable. This research proposes a framework that adopts a semi-structured data integration approach using a data view mechanism and XML and XPath standards. A prototype of the framework is designed and implemented using a loosely-coupled mediator-agent-adapter architecture based on distributed component technology. An XML query language provides the basis for data view definition as well as query specification and transformation. A denotational semantics and an abstract syntax of the query language are defined here to provide a formal basis for implementation of query processing and logical query optimization. The mapping between the concrete XML syntax and the abstract syntax of the query language is defined to facilitate implementation of query processing. The XMark benchmark for XML databases is used to assess the functionality and performance of the prototyped implementation of the query language and system. The benchmarking result and analysis establish a base line query performance measure for the proposed data integration framework and identify the characteristics of different system implementations.

The emerging application-to-application paradigm allows an organization's data to be shared across applications in both intra-enterprise and inter-enterprise contexts. In order to seamlessly integrate information from disparate, heterogeneous, and multi-organizational applications and quickly adapt to new application contexts, rigid information modeling and proprietary data representation technology have proven inadequate. Conventional data integration approaches are based on database systems that represent data semantics using static structured data schemas. They cannot provide adequate facilities to satisfy the increasing need for effective and efficient application data integration from heterogeneous data sources. Applications need to be built on an information model that is standards-based, flexible, and adaptable. This research proposes a framework that adopts a semi-structured data integration approach using a data view mechanism and XML and XPath standards. A prototype of the framework is designed and implemented using a loosely-coupled mediator-agent-adapter architecture based on distributed component technology. An XML query language provides the basis for data view definition as well as query specification and transformation. A denotational semantics and an abstract syntax of the query language are defined here to provide a formal basis for implementation of query processing and logical query optimization. The mapping between the concrete XML syntax and the abstract syntax of the query language is defined to facilitate implementation of query processing. The XMark benchmark for XML databases is used to assess the functionality and performance of the prototyped implementation of the query language and system. The benchmarking result and analysis establish a base line query performance measure for the proposed data integration framework and identify the characteristics of different system implementations.

The two-volume set LNCS 3032 and LNCS 3033 constitute the thoroughly refereed post-proceedings of the Second International Workshop on Grid and Cooperative Computing, GCC 2003, held in Shanghai, China in December 2003. The 176 full papers and 173 poster papers presented were carefully selected from a total of over 550 paper submissions during two rounds of reviewing and revision. The papers are organized in topical sections on grid applications; peer-to-peer computing; grid architectures; grid middleware and toolkits; Web security and Web services; resource management, scheduling, and monitoring; network communication and information retrieval; grid QoS; algorithms, economic models, and theoretical models of the grid; semantic grid and knowledge grid; remote data access, storage, and sharing; and computer-supported cooperative work and cooperative middleware.

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