Finding information in large scale autonomous heterogeneous databases is an issue that has been virtually unexplored in database research. We describe a new approach for finding information in a large scale network of autonomous and heterogeneous databases. In our scheme, no a priori knowledge of the database schemas or the space of information is necessary to locate information. The system relies on an object-oriented architecture to educate users about the available space of information and help them locate information sources. The system, named FINDIT, accommodates database autonomy as well as heterogeneity by separating the education of users about and finding information sources from the actual manipulation thereof. To ensure information abstraction and encapsulation, the system is divided into three categories, namely, user servers, database servers, and databases. User servers are geared towards satisfying users needs while database servers are in charge of managing databases. 1...

Distributed database technology is expected to have a significant impact on data processing in the upcoming years. With the introduction of commercial products, expectations are that distributed database management systems will by and large replace centralized ones within the next decade. In this paper, we reflect on the promises of distributed database technology, take stock of where we are, and discuss the issues that remain to be solved. We also present new research issues, such as distributed object-oriented systems, distributed knowledge bases, multiprocessor data servers, and distributed multidatabase systems, that arise with the introduction of new technology and the subsequent relaxation of some of the assumptions underlying current systems. Keywords: distributed database, data distribution, transaction management, distributed query procesing, object-oriented system, knowledge base, multidatabase system. * An abridged version of this paper has appeared as "Distributed Databas...

Sharing data among disparate databases has so far mostly been achieved through some form of ad--hoc schema integration. This approach becomes less tractable as the number of participating database grows. Therefore, the complexity of making autonomous heterogeneous databases interoperate is dependent on adequately addressing the autonomy and heterogeneity issues. In this paper, we describe a prototype that implements an approach which addresses these issues in the context of large multidatabase systems. In particular, we describe a scheme that builds a Hyperdistributed Database using a two--staged approach. We also describe how conglomerations databases are formed, modified, and evolved. Keywords: Multidatabases, Federated Databases, Interoperable Heterogeneous and Autonomous Databases, Query Languages. 1 Introduction The past few decades have witnessed an explosion in the number of databases. With this increase, there has been a renewed interest in sharing information across heterogen...

Hypertext is a simple concept for organizing information into a graph structure of linked container objects. This paper examines issues involved in applying hypertext concepts to the integration of heterogeneous, autonomous software repositories, and presents a solution called the Distributed Hypertext System (DHT). Based on a hypertext data model and client-server architecture, DHT features powerful modeling capabilities, integration of heterogeneous, preexisting repositories, update with concurrency control, and full local autonomy. 1 Introduction Considerable research has been devoted to software object management. Table 1 summarizes some of the results. For the most part, these efforts assume that the objects in the repository are stored in a central database or storage manager, which may be accessed by distributed clients. In reality, however, software artifacts may be stored in many diverse locations under independent control. This may happen due to multi-contractor development...

This paper describes a strategy for the construction of large-scale heterogeneous systems which combines the benefits of both tight-coupling systems (insulating users from the complexity of semantic heterogeneity thus promoting greater usability) and loose-coupling systems (allowing changes in individual components to be contained locally thus assuring the long-term viability of the system as a whole). We define anew data model (coin) based on a deductive and object-oriented language with which knowledge of data semantics is represented in the form of enriched schemas, contexts and underlying domain models. Query mediation in this framework is driven by a top-down evaluation strategy which yields a query plan describing what sources are used and what conversions must be applied in mediating semantic con icts. The coin data model induces a novel dichotomy between schemas and contexts thus permitting knowledge of data semantics to beshared and reused across different systems in similar environments. This in turn provides various options for querying disparate sources, with each offering a different level of transparency depending onthe needs of the users. The richness of the model offers receivers more flexibility, both in defining what disparities should count as conflicts, and how conflicts should be resolved.

Research and development in the FIDE project on Fully Integrated Data Environments has led to the concept of Persistent Object Systems (POS) which generalize database systems by re-interpreting schemas as type definitions and databases as typed variables in addition to treating lifetime as a type-independent property. Furthermore, FIDE develops uniform linguistic interfaces for data modelling, computation and communication, and extends database, programming and communication technology to enable integrated application development based on interoperating POSs. As a consequence of such...

Motivation: Molecular biology databases have been proliferating rapidly. Their heterogeneity and complexity pose a great challenge to efforts in database interoperation. To minimize the efforts of interoperating heterogeneous databases, it is useful to develop a system that lets a user of a particular genomic database access another related database as if the latter is structurally similar to the former. Results: We extend a structurally simple model—the entity– attribute–value (EAV) model—to describe uniformly metadata relating to individual databases. Such metadata, which are necessary for performing database comparisons, include descriptions of primitive database objects (including entities, attributes, domain values and entity relationships) and specification of correspondences among the database objects. We show how to decompose SQL queries and map them from one database to another based on the EAV representation of the basic database objects. A prototype system is implemented to demonstrate query interoperation between two chromosome map databases. Availability: Freely available (Cold Fusion source code and an Access database containing the mapping knowledge) upon request from the author.

Formulating queries to access multiple databases can be a formidable task, especially when many terms from various databases and complex constraints are involved. To specify a multidatabase query, the user usually has to search through documents for exact database terms and learn the multidatabase language. This report presents QUICK (QUery Interface to CPL-Kleisli), a graphical user interface to multiple databases. CPL is a high-level multidatabase language built on top of an open query system Kleisli. QUICK allows users to handle overwhelming information from different data sources in an intuitive and uniform manner. The query specification is reduced to specifying user's terms in his/her own world, selecting paths and specifying constraints in a graph. QUICK is able to automatically generate a CPL query that corresponds to the user's intent. 1 Introduction A multidatabase system is a distributed system that acts as a front end to many autonomous DBMSs through a global schema or a ...

Formulating queries to access multiple databases can be a formidable task, especially when many terms from various databases and complex constraints are involved. To specify a multidatabase query, the user usually has to search through documents for exact database terms and learn the multidatabase language. This report presents QUICK (QUery Interface to CPL-Kleisli), a graphical user interface to multiple databases. CPL (Collection Programming Language) is a high-level multidatabase language built on top of an open query system Kleisli. QUICK allows users to handle overwhelming information from different data sources in an intuitive and uniform manner. The query specification is reduced to specifying user's terms in his/her own world, selecting paths and specifying constraints in a graph. Through the terms entered by the user, QUICK is able to reduce the scope of the views and paths to only those that are relevant to answering the user's query. Furthermore, QUICK is able to ...

The main contribution of this work is the development of a Metadata Manager to interconnect heterogeneous and autonomous information sources in a flexible, expandable and transparent way. The interoperability at the semantic level is reached using an integration layer, structured in a hierarchical way, based on the concept of Mediators. Services of a Mediator Metadata Manager (MMM) are specified and implemented using functions based on the Outlines of GOA++. The MMM services e are available in the form of a GOA++ API and they can be accessed remotely via CORBA or through local API calls. Brugger et al.,Mediators Metadata Management Services, 2(1) 30-47(1999) 31 1 Introduction During the last years, a great research effort has been directed to the integration of Heterogeneous and Distributed Database Systems (HDDS) (BUKHRES, 1996). HDDS provide transparent and simultaneous access to independent databases using one single data manipulation and definition language. The impleme...