Previous projects


PICSEL 1 project | PICSEL 2 project



The approach which has been chosen in PICSEL 1 is to define an information server as a knowledge-based mediator in which CARIN is used as the core logical formalism to represent both the domain of application and the contents of information sources relevant to that domain. CARIN combines the expressive power of rules and the ALN description logics. The expressive power of the CARIN language is exploited in the PICSEL information integration system, while maintaining the decidability of query answering.
PICSEL 1 contains a cooperative module to refine queries posed to a mediator which gets no answer.

The general architecture is shown below :









In PICSEL 2, we have focused on the automation of the construction of an ontology in the context of a domain-specific mediator querying XML documents. The ontology that we want to build is a schema based on classes. The approach is based on the DTDs associated to the XML documents. Besides, we have designed mediation systems which integrate services on the Web in order to make them usable to final users. As services on the Web are numerous and heterogeneous, as they must sometimes be combined to satisfy final users requirements, interfaces giving the illusion of a convivial, unique, centralized and homogeneous access are also necessary. We have proposed to use a mediator approach to design such an interface and we have emphasized the principles to make the mediator approach applicable in this context. The first principle is a solution to semantic heterogeneity. It exploits results in standardization relative to business transactions. The second principle concerns the scalability of the mediator approach. It emphasizes two points : decoupling of the various components and strong mediation. We have proposed an architecture of a mediation system integrating services, designed in the setting of the PICSEL 2 project. We have illustrated this approach with an application of e-commerce in the tourism domain.

In PICSEL 2, we have also designed a user interface, the OntoRefiner system, for helping the user to navigate numerous retrieved documents after a search querying a semantic portal which integrates a very important number of documents. Retrieved answers are filtered and the user could be provided only with the answers which are, according to him, the most relevant. The refinement process is based on two technologies, dynamic clustering close to Galois lattice structure combined to the use of a domain ontology. The Galois lattice structure provides a sound basis for the query refinement process. However, its construction as a whole is a very costly process. So, we have proposed an approach based on the use of a domain ontology, avoiding the construction of the whole Galois lattice


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Last modification : Tuesday, March 7th 2006