Ralf Nikolai

Thesaurus federations: loosely integrated thesauri for document retrieval in networks based on Internet technologies

Abstract As a result of the distribution of interrelated information over several different information systems, the interconnection of information systems has increased in recent years. However, a purely technical interconnection is insufficient for users who need to find their way to information they are looking for. Thesauri are a proven means to identify documents, e.g., books of interest in a library. For different domains, different thesauri are available, which can be used in information systems as well, e.g., for the indexing and retrieval of data objects. Thus, the interconnection of information systems raises the need to integrate related thesauri. Furthermore, recent advances in open interoperability technologies (World Wide Web, CORBA, and Java) offer the potential for completely new technical solutions for employing thesauri.This paper presents an approach for integrating multiple thesaurus databases. It concentrates on the integration of distributed and heterogeneous thesaurus databases and the integration of multilingual and monolingual thesauri. The software architecture takes advantage of the most advanced Internet and CORBA technology currently available in public domain and in commercial implementations.

Thesaurus federations: a framework for the flexible integration of heterogeneous, autonomous thesauri

Modern information systems such as the World Wide Web and digital libraries contain more data than ever before, are globally distributed, are easy to use, and therefore become accessible to huge, heterogeneous user groups. On the other hand, the potentially enormously large amount of heterogeneous information requires powerful tools to allow the user to find relevant pieces of data. One such tool is thesauri. They are a proven means to provide a uniform and consistent vocabulary for the indexing and retrieval of information-bearing objects (IBOs). Modern multi-lingual and multi-subject information systems require more than the traditional single-language, narrow-focus thesauri. The broad clientele of information systems demands thesauri that can be used by non-specialists. To achieve this goal, we introduce the framework of thesaurus federations, i.e. loose compounds of distributed, multi- or mono-lingual thesauri that go beyond the already-known concepts of multi-thesaurus systems. We classify multi-thesaurus systems into multi-thesaurus environments, thesaurus switching systems and thesaurus compounds. Our architecture is based on a mediation layer and wrappers for the integration of heterogeneous, distributed thesauri. We present a Java-based prototype system which enables integrated access to several thesauri, which is available through a SQL or HTML interface via a comfortable thesaurus federation browser. This system has been used for the retrieval of metadata records managed by the Catalogue of Data Sources of the European Environment Agency (EEA).

Data and Metadata Management in Distributed Environmental Information Systems

Data related to a certain natural area, e.g. the Mediterranean Sea, the Alps or the Danube river, is often collected at different sites in different countries. Taking the availability of public computer networks like the Internet into account, it comes to no surprise that public authorities, scientists, and the general public would like to access such data that is managed at different sites transparently and homogeneously. The creation of an appropriate information technology infrastructure raises several conceptual and technological questions, e.g., responsibilities of data collection and quality assurance, searching of inhomogeneous databases in a multilingual environment and technologies for distributed, heterogeneous, scalable information systems.

Multidimensional access to European environmental data

Catalogues have been an indispensable tool to locate books in libraries for centuries. Their equivalent in our networked world are catalogue systems which facilitate search and retrieval especially on the Web. We explore the requirements and their technical solutions to support search and retrieval according to multiple dimensions in Web based catalogue systems. We show how components that address individual dimensions can also be combined to tackle multidimensional queries. Several European environmental catalogue systems that we have been involved in are used as examples to illustrate the approach which can easily be transferred to further application e.g., e-commerce.