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Computer

Issue 12 • Date Dec. 1991

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Displaying Results 1 - 8 of 8
  • Classifying schematic and data heterogeneity in multidatabase systems

    Page(s): 12 - 18
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (729 KB)  

    A complete framework for enumerating and classifying the types of multidatabase system (MDBS) structural and representational discrepancies is developed. The framework is structured according to a relational database schema and is both practical and complete. It was used to build the UniSQL/M commercial multidatabase system. This MDBS was built over Structured-Query-Language-based relational database systems and a unified relational and object-oriented database system named UniSQL/X. However, the results are substantially applicable to heterogeneous database systems that use a nonrelational data model (for example, an object-oriented data model) as the common data model and allow the formulation of queries directly against the component database schemas.<> View full abstract»

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  • The Pegasus heterogeneous multidatabase system

    Page(s): 19 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (961 KB)  

    Pegasus, a heterogeneous multidatabase management system that responds to the need for effective access and management of shared data across in a wide range of applications, is described. Pegasus provides facilities for multidatabase applications to access and manipulate multipole autonomous heterogeneous distributed object-oriented relational, and other information systems through a uniform interface. It is a complete data management system that integrates various native and local databases. Pegasus takes advantage of object-oriented data modeling and programming capabilities. It uses both type and function abstractions to deal with mapping and integration problems. Function implementation can be defined in an underlying database language or a programming language. Data abstraction and encapsulation facilities in the Pegasus object model provide an extensible framework for dealing with various kinds of heterogeneities in the traditional database systems and nontraditional data sources.<> View full abstract»

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  • Failure-resilient transaction management in multidatabase

    Page(s): 28 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (982 KB)  

    Failure recovery in a multidatabase environment is addressed. It is shown that local autonomy considerations force the designer of a multidatabase system to trade off certain desirable properties to achieve reliability for transaction management. Representative techniques in the research literature are contrasted and compared. The author's approach to the problem is described.<> View full abstract»

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  • Integrating diverse information repositories: a distributed hypertext approach

    Page(s): 38 - 45
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    The authors address key problems of support for multiple, heterogeneous repositories, each under separate and autonomous administration with a variety of incompatible interfaces; diverse, unconventional data types; and different ways of viewing relations among the same information items. They present a solution to these problems that is radically different from existing systems. It is based on their distributed hypertext (DHT) architecture, which combines transparent access to autonomous, heterogeneous information repositories and a powerful, flexible organization technique. This approach requires no change to the structure or content of participating repositories.<> View full abstract»

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  • Specifying interdatabase dependencies in a multidatabase environment

    Page(s): 46 - 53
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    The problem of interdatabase dependencies and the effect they have on applications updating interdependent data are addressed. A model that allows specifications of constraints among multiple databases in a declarative fashion is proposed. The separation of the constraints from the application programs facilitates the maintenance of data constraints and allows flexibility in their implementation. It allows investigation of various mechanisms for enforcing the constraints, independently of the application programs. By grouping the constraints together, it is possible to check their completeness and discover possible contradictions among them. The concepts of polytransactions, which use interdatabase dependencies to generate a series of related transactions that maintain mutual consistency among interrelated databases, is discussed.<> View full abstract»

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  • Resource integration using a large knowledge base in Carnot

    Page(s): 55 - 62
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    A method for integrating separately developed information resources that overcomes incompatibilities in syntax and semantics and permits the resources to be accessed and modified coherently is described. The method provides logical connectivity among the information resources via a semantic service layer that automates the maintenance of data integrity and provides an approximation of global data integration across systems. This layer is a fundamental part of the Carnot architecture, which provides tools for interoperability across global enterprises.<> View full abstract»

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  • Heterogeneous and autonomous transaction processing

    Page(s): 64 - 72
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    The problems specific to heterogeneous and autonomous transactions processing (HATP) systems are discussed. HATP is divided into three dimensions: distribution, heterogeneity, and autonomy. The authors regard the three dimensions as independent, and they present concrete design and implementation techniques to support this view.<> View full abstract»

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  • SQL Access: an implementation of the ISO Remote Database Access Standard

    Page(s): 74 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB)  

    As an enterprise begins tying heterogeneous systems into a single information system, it encounters the difficult task of interfacing different platforms running different operating systems, network protocols, and data management systems. Bringing all these elements together into a coherent information resource can require substantial effort and might result in a system that needs the interfaces reworked every time a new platform or product is introduced into the system. To address these issues, the International Organization for Standardization has drafted the Remote Database Access Standard to provide a protocol that can be universally accepted, implemented, and validated, and thereby provide users with a single, well-defined interface for heterogeneous environments. Based on a client-server architecture, RDA uses well-defined Open Systems Interconnect services as the basis for the RDA services.<> View full abstract»

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Computer, the flagship publication of the IEEE Computer Society, publishes highly acclaimed peer-reviewed articles written for and by professionals representing the full spectrum of computing technology from hardware to software and from current research to new applications.

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Ron Vetter
University of North Carolina
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