The dif"cult problems in the design of systems which facilitate interoperation and mediation among information sources and their consumers arise from the presence of semantic heterogeneity among the schemas and ontologies supporting the different services. The purpose of this paper is to develop a taxonomy of semantic heterogeneity, and to describe, taking the perspective of text databases, the conditions under which autonomy-respecting interoperation of different kinds are likely to be feasible. The main conclusion is that interoperation can be based on structured database technology only if the participating organizations communicate among themselves, otherwise the considerations underlying text databases dominate the technology used. 1.

Schema integration is the basis for successfully building a database federation. Current proposals directly integrate the different schemata using a semantical powerful data model, for example an extended ER model or an object-oriented model. We propose instead to use for integration a semantical poor model and build semantically rich representations as external views only. This approach enables a flexible integration and derivation especially for inheritance trees. We present an algorithm enabling the derivation of different inheritance trees as external views onto an integrated schema. The resulting inheritance tree can be influenced by giving priorities to input classes or attribute combinations and satisfies several formalized quality criteria for external views. Keywords: database federation, schema integration, view derivation, inheritance hierarchy, extensional and intensional conflicts 1 Introduction The integration of heterogeneous schemata and the derivation of views is an ...

. In this paper we discuss the use and treatment of integrity constraints in the federated database design process. We consider different situations occurring frequently in the schema transformation and schema integration process. Based on that, general rules are given which describe the correct treatment of integrity constraints. Other proposed integration approaches do not consider integrity constraints at all or are restricted to special kinds of constraints. Therefore, our approach can be used to extend or complete existing integration methodologies. 1 Introduction Considering the current situation in enterprises we can discover that many different information systems are used in different parts of the enterprise. Furthermore, there is an increasing need to get a uniform access to the heterogeneous databases lying behind those information systems. The aim is to obtain a federated database system in the sense of [SL90]. Besides a uniform access to data stored in different d...

The amount of information available throughout the Internet or through specific collections is so huge that more and more sophisticated information handling systems are necessary to exploit it. In addition to efficient retrieval engines, the users need some tools to be able to analyse the relevant information without having to read all of it. Knowledge Discovery Systems main objective is to turn some selected pieces of raw information into knowledge or generalized patterns. Such a process includes a lot of problems to solve all over the three knowledge discovery phases: information harvesting and selection, information mining, results displaying. In this paper we present an interactive method to achieve knowledge discovery. It is based on information harvesting, homogenization and filtering. The discovery process itself is achieved making several modules cooperate : different mining functions and visualization modules dynamically interact-directed by the user. The operational software ...

The problem of connecting together a number of different databases to produce an integrated information system has attracted a considerable amount of attention over the years and various approaches have been developed to handle this. However, the general problem of gathering related information from a number of existing heterogeneous databases is complex because of the differences in representation and meaning of data in different data sets. Many different approaches have been described to resolve this problem, and some prototype systems built. However, it is difficult to compare the effectiveness of different approaches and prototypes. This paper is aimed at addressing the specific issue of assessing the generality of different approaches. To this end it presents a framework for classifying the differences between data in different databases and a test-suite which can be used to evaluate and compare the extent to which different approaches handle different aspects of this heterogeneit...

Merging inheritance hierarchies is an essential task of schema integration as part of the design of a federated database. Based on the formalization of inheritance hierarchies as concept lattices we present an efficient algorithm for deriving an integrated inheritance hierarchy as result of merging two inheritance hierarchies with overlapping extensions and types. Several methods are presented to modify the integrated hierarchy to optimize the resulting object-oriented schema with respect to certain quality criteria (disjoint specialization, number of classes, support of null values, etc). These methods are necessary to adjust the integrated schema to specific requirements and for realizing applicationspecific views. Keywords: federated database design, schema integration, inheritance hierarchy, concept lattices CONTENTS i Contents 1 Introduction 1 2 Example Scenario 3 3 Concept Lattices 7 4 A Practicable Algorithm 11 5 Application to the Example 13 6 Transformation of Inheritance...

In this paper we present an approach towards a unified modeling and query-processing tool for mediatory information systems. Based upon Coloured Petri-nets we are able to model the integration of parametric data (external, uncertain and temporal informations) and visualize the dataflow in mediatory information systems. Keywords: Coloured Petri-nets, Interoperable federated systems, Parametric Databases, Deductive Databases 1 Introduction With the transition from isolated to cooperating information systems there is an urgent need for sound computational query-processing with a diversity of circumstantial informations. Wiederhold et al. [27, 25, 26] have proposed the concept of a mediator, a device which expresses how the integration of different information systems is to be achieved. Different languages for building mediatory information systems have been presented in [17, 15, 12]. These approaches depart from former proposals as they are declarative, i.e. logic based. We believe...

The amount of information available in organisation internal information systems or in international networks such as Internet is growing at an important rate. As a consequence, more and more sophisticated information management systems are needed. Among the functionalities of those systems, information retrieval is one of the key elements. It allows one to find the relevant information according to its needs. Because of the amount of retrieved information, it is less and less possible to manually analyse it. That is why new systems functionalities needs have recently appeared. The objective is to automate as much as possible the transformation of the retrieved information (raw information) into knowledge or generalised patterns (hidden information). That new computed information could then be used directly by the users (manufacturers, searchers,...) to have an overview of the area they are interested on and to take the relevant decisions. One of the main applications is monitoring of...

A key problem in providing enterprise-wide information is the integration of databases that have been independently developed. A major requirement is to accommodate heterogeneity and at the same time preserve the autonomy of component databases. This article addresses this problem and presents a strategy to integrate heterogeneous OO schemas. As compared to the existing methodologies, this approach integrates local schemas into a deduction-like global schema. In this way, more semantic relationships of component schemas can be captured, and more complete integration can be obtained. In addition, an efficient algorithm is proposed which can do the integration almost automatically, based on the correspondence assertions supplied by designers. This algorithm is efficient in the sense that the characteristics of assertions are utilized to avoid useless matchings.

A large scaled network may consist of hundreds of disparate and autonomous databases. Users in such an information-providing environment usually access information from those databases in the same or similar application domains so that there is no need to handle all the entities from all the databases. That is, in most cases, only a subset of databases is required for the users' requests. As the number of databases increases, the need to manage such a network of databases increases. In this paper, we present a split/cluster approach using the object-oriented technique to allow users to incrementally and dynamically access the information they want without being overwhelmed with all of the unstructured information. The approach is based on the affinity relationships of the databases and is performed recursively to split these databases into clusters. Then a cluster hierarchy is formed to provide different levels of abstractions for the users. This framework provides a flexible means of...