Découverte des services dans les systèmes d'information géographiques répartis sous réseau ad-hoc

摘要

The actual geographic information systems today provide access to a large number of udheterogeneous and distributed sources. The multiplication of resources and increased data requires udthe use of Web services that appear as a solution to ensure interoperability between different udresources. They are able to collaborate and share control of process data and information between udapplications on different platforms. ud The use of geographic data through Web services shows the geospatial Web Services (GWS). udA growing number of GWS designed to interoperate spatial information over the network have udemerged. GWS are changing the way in which spatial information systems and applications are uddesigned, developed, and deployed. When GWS is increasing, the difficulty of the service discovery udincreases too. The service discovery represents one of the interactions between Web service udcomponents (supplier, customer and UDDI). It is unfortunately that it is based only on the syntax. udThe semantic aspect necessary to satisfy the user is absent. The use of semantic Web technology in udthe Web service discovery phase gives rise to the Web service semantic discovery. The latter is udbased on semantic reasoning. It enhances the accuracy of search results compared to traditional udtechniques of Web service discovery, the additional matching accuracy in terms of computing udpower. In this paper we are interested to the distributed GWS semantic discovery based on udgeographical metadata held in geo-catalogs. The metadata used in our case is designed according udto the ISO 19119 standard reinforced by the quality criteria. ud The suggested approach is Geospatial Web services semantic discovery using metadata and udmulti-agents system. It is based on the co-operation of a set of agents using the semantic capacities udof the geospatial Web service through the catalogues based on the metadata according to standard udISO19119. The agents of our architecture take in account the principal properties of the agent udtechnology (Portability, Autonomy, Stability, Persistence, Flexibility, and Sociability). The based udidea of our approach is to classify to geospatial Web services by functionalities by using metadata udof ISO 19119 standards. ud Optimization of the recent approach is done by using quality and personalization. Quality udmanagement plays a vital role to satisfy the user needs (explicit or implicit). Personalization aims udto facilitate the expression of user needs and make information intelligible to the selected user and udexploitable. Our discovery approach based on semantic metadata organized in catalogs, proposed udin the publication phase of GWS two levels of description. The first level concerns the GWS classes udcatalog based on the ISO19119 standards and quality criteria; the second level concerns the UDDI udregistry through the WSDL. In the discovery phase, this solution allows to restrict the search space udand increase the number of relevant services through the application of the algorithm of ud"matching". In the metadata level, the matching algorithm “LARKS” is adjusted by applying the udfirst three filters (context, profile, similarity) on the quality criteria contained in the request and uddescription of classes available in GWS metadata catalog. This solution enables us to have a result udlike "relaxed match”. In the UDDI registry level, the application of “Matching” algorithm is based udon the interrogation mechanism of the UDDI registry using the different pages (White pages, yellow udpages, green pages). A list of GWS classified by order of correspondence (quality aspect, functional udaspect) is the result of the discovery. ud For the implementation of our approach, we propose the tourism field as application uddomain; we use a prototype ontology which includes only the part of the terminology field of udtourism. We develop a Web application, an adaptation of a traditional Web architecture. Our udimplementation is based on the use of metadata and the algorithm of "matching". To make these udpersistent metadata, we chose the pair XML / XML Schema, based on the principle of markup udlanguages SGML family. A set of interface is available to the user (Provider /Customer / User), the udinterface is made using PHP that provides ease of interfacing with databases. These interfaces are: ud1. Interfaces for acquiring knowledge of the user profile; ud2. GWS publication interfaces; ud3. GWS discovery interfaces.