Semantic Integration and Interoperability among Portals

INTRODUCTION In distributed settings, such as this of the WorldWide Web , where a large number of information sources and services reside, portals provide a single point of global access via a single and unified view. This view is circumscribed by a specific conceptualization and a specific vocabulary whose entries provide lexicalizations of the concepts used for shaping information, data, and services provided. Ontologies play a key role to shaping information as they provide conceptualizations of domains. Different portals may use different or partially overlapping ontologies for shaping information, or even different schemata for storing data. This affects the integration of information from different portals, and/or the interoperability between the services that portals provide. Consequently, this situation affects recall and precision of information retrieval, and sets limitations to the composition (and decomposition) of services among portals for serving clients' (users or software agents) requests. Semantic integration refers to the set of problems that appear between disparate information sources and concern matching ontologies or schemas, detecting duplicate tuples, reconciling inconsistent data values, and reasoning with semantic mappings. The goal is to integrate information and data under a single view, preserving the semantics of the sources. Service invocation in a distributed and open setting involves discovering the appropriate services, selecting among a set of candidates that match the requirements of the client, interacting with the selected service and interpreting service replies. Much of the work to be done towards services' interoperability concerns publishing semantic service descriptors which clients will readily exploit. The goal is for software agents to discover, interact with, and fetch the results of services automatically. Both problems concern the mapping, aligning, translating and merging ontologies. This article aims to provide a review to the techniques for semantic integration and interoperability of portals by exploiting ontologies. It does not aim to provide an in-depth and exhaustive presentation of the existing approaches 1-there exist some excellent surveys on the methods and techniques proposed, for instance in Shvaiko & Euzenat (2005) or in Noy (2004), but to provide definitions and a roadmap to the existing research efforts towards this exciting research topic which is of much importance for any web user, community, enterprise, organization and government.