European Journal of Scientific Research - EuroJournals

Generic Architecture Based Agent for Context and Schema Mediation 379
2. The comparison of ontologies and the automatic generation of the mapping rules of the
schemas between an intelligent agent consuming (IAC) and another intelligent agent
supplier (IAS), the principal steps are:
a. To compare the ontology of the IAC with the ontology of the IAS. The classes of two
ontologies are compared using a semantic distance (the calculation of the semantic
distance between two classes is calculated starting from elementary calculations of
distances which takes into account the various elements of the environment [24] from a
class in its ontology). The identified classes as equivalent are retained for the
reconciliation process.
b. To adapt useful information of the IAS ontology in the IAC ontology. Sub schema
dependent on the equivalent classes of the IAS ontology is dependent on the classes of
the IAC ontology.
c. Generation of the mapping rules which make it possible to bind information been
essential in order to ensure the static query resolution.
3. Reformulation of the query Q, which consists in reformulating the query in terms of
ontology.
4. It translates the query Q coming from other IACs into query Q' expressed in the proper
language of handling of the local base of the supplier.
5. Filtering of the results.
• Routing agents
They are multi-domain agents, gathering the nearest semantically domain. The roles of a
routing agent are:
1. To gather the nearest semantically intelligent agents in a net contacts to be used as
suppliers.
2. To ensure the dynamic query resolution, and to communicate with other routing agents for
execute reformulated queries.
3. To record/eliminate dynamically the agents which take part in the cooperation.
To search intelligent agents which contain information to which the domain is nearest to the
domain of an intelligent agent (consuming).
3.4. Adding a new information system
The integration phase, of a new information system within the proposed mediation system, begins with
creation from an intelligent agent and continues with the fastening of this last to a routing agent which
is nearest semantically.
The intelligent agent applies the Contract Net protocol. The intelligent agent sends an invitation
to tender describing its domain. The routing agents receiving the call provide their ability (semantic
proximity rate). Once that the intelligent agent receives answers of all the routings agents, it evaluates
these rates and makes its choice on a routing agent which is nearest semantically. The chosen routing
agent, adds the intelligent agent to its net contacts.
3.5. Description of the proposed mediation model
The use of a common representation model ensures on the one hand the comprehension of the
information schema and on the other hand a uniform access to the whole of the distributed data. The
majority of the studies on the distributed and heterogeneous data management systems use the
relational model or the object model like integration data model [16].
Our approach is to use the OWL (Web Ontology Language) like common data model and we
base on work [17] which uses OWL like ontologies representation model. The OWL enriches the RDF
Schemas model by defining a rich vocabulary for the description of complex ontologies. So it is more
expressive than RDF and RDFS, which some reproach an insufficiency of expressivity due to the only
definition of the relations between objects by assertions. OWL brings also a better integration, an