We address the problem of providing integrated access to diverse and dynamic information sources. We explain how this problem differs from the traditional database integration problem and we focus on one aspect of the information integration problem, namely information exchange. We define an object-based information exchange model and a corresponding query language that we believe are well suited for integration of diverse information sources. We describe how, the model and language have been used to integrate heterogeneous bibliographic information sources. We also describe two general-purpose libraries we have implemented for object exchange between clients and servers.

One of the main tasks of mediators is to fuse information from heterogeneous information sources. This may involve, for example, removing redundancies, and resolving inconsistencies in favor of the most reliable source. The problem becomes harder when the sources are unstructured/semistructured and we do not have complete knowledge of their contents and structure. In this paper we show how many common fusion operations can be specified non-procedurally and succinctly. The key to our approach is to assign semantically meaningful object ids to objects as they are "imported " into the mediator.

Due to the proliferation of database applications, the integration of existing databases into a distributed or federated system is one of the major challenges in responding to enterprises' information requirements. Some proposed integration techniques aim at providing database administrators (DBAs) with a view definition language they can use to build the desired integrated schema. These techniques leave to the DBA the responsibility of appropriately restructuring schema elements from existing local schemas and of solving inter-schema conflicts. This paper investigates the assertion-based approach, in which the DB~s action is limited to pointing out corresponding elements in the schemas and to defining the nature of the correspondence in between. This methodology is capable of: en-suring better integration by taking into account additional semantic information (assertions about links); automatically solving structural conflicts; building the integrated schema without requiring conforming of initial schemas; applying inte-gration rules to a variety of data models; and performing view as well as database integration. This paper presents the basic ideas underlying our approach and focuses on resolution of structural conflicts.

Mediators are used for integration of heterogeneous information sources. We present a system for declaratively specifying mediators. It is targeted for integration of sources with unstructured or semi-structured data and/or sources with changing schemas. We illustrate the main features of the Mediator Specification Language (MSL), show how they facilitate integration, and describe the implementation of the system that interprets the MSL specifications.

Abstract A multidatabase system (MDBS) is a confederation of pre-existing distributed, heterogeneous, and autonomous database systems. There has been a recent proliferation of research suggesting the application of object-oriented techniques to facilitate the complex task of designing and implementing MDBSs. Although this approach seems promising, the lack of a general framework impedes any further development. The goal of this paper is to provide a concrete analysis and categorization of the various ways in which object orientation has affected the task of designing and implementing MDBSs.

The objective of entity identification is to determine the correspondence between object instances from more than one database. This paper examines the problem at the instance level assuming that schema level heterogeneity has been resolved a priori. Soundness and completeness are defined as the desired properties of any entity identification technique. To achieve soundness, a set of identity and distinctness rules are established for entities in the integrated world. We propose the use of extended key, which is the union of keys (and possibly other attributes) from the relations to be matched, and its corresponding identity rule, to determine the equivalence between tuples from relations which may not share any common key. Instance level functional dependencies (ILFD), a form of semantic constraint information about the real-world entities, are used to derive the missing extended key attribute values of a tuple. 1 Introduction Database integration is the problem of taking two (or mor...

Object-oriented databases (OODBs) are believed to more naturally reflect the behavior and organization of complex application domains. The schema consists of a collection of classes, organized into hierarchies which nicely organize abstractions over the domain. Objects are created as instances of classes, encapsulating data and interpretation of data together. An important characteristic is the support for evolutionary programming, and so that existing programs may be extended with new classes without affecting other parts of the system.

Scientific discovery in data rich domains (e.g., biological sciences, atmospheric sciences) presents several challenges in information extraction and knowledge acquisition from heterogeneous, distributed, autonomously operated, dynamic data sources. This paper describes these problems and outlines the key elements of algorithmic and systems solutions for computer assisted scientific discovery in such domains. These include: ontology-assisted approaches to customizable data integration and information extraction from heterogeneous, distributed data sources; distributed data mining algorithms for knowledge acquisition from large, distributed data sets which obviate the need for transmitting large volumes of data across the network; ontology-driven approaches to exploratory data analysis from alternative ontological perspectives; and modular and extensible agent-based implementations of the algorithms within a platform-independent agent infrastructure. Prototype implementations of ...

this report from s2 also. In this case, all we have to do is replace (R6.2) with the following rule.

We have developed the Transparent Schema Evolution (TSE) system that, simulating schema evolution using object-oriented views, allows for the interoperability of applications with diverse and even changing requirements. TSE relieves users of the risk of making existing application programs obsolete when run against the modified schema, because the old view schema is maintained while a new view schema is generated to capture the changes desired by the user. However, TSE may be generating a large number of schema versions (object-oriented view schemata) over time, resulting in an excessive build-up of classes and underlying object instances - some of which may potentially no longer be in use. In this paper, we propose to solve this problem by developing techniques for effective and consistent schema removal. First, we characterize four potential problems of schema consistency that could be caused by removal of a single virtual class; and then outline our solution approach for each of t...