3. SEMANTIC RECONCILIATION
3.1 Principe
In PMDMS, each peer (e.g. Pj ) describes its data in a con-
crete DTD (e.g. PCo
j ) representation and exports it in an ex-
pertise table. Additionally, every node ni is associated with
a set syn(ni) of keywords (essentially synonyms added by
the user of the peer Pj in the ontology POwl
j at design-time)
which provides more linguistic information about the node
to guide mapping discovery. To discover semantics equiva-
lences (i.e. similar concepts) between expertise of peers, the
MatchMaker is designed with two principal components: 1.
the ¯rst one is the wrapper. It extracts concepts of each
received expertise and matches them with concepts pub-
lished by the peer in its POwl
j (i.e. ontology.owl). After
that, the wrapper transform the obtained schema (that as-
sociates each concept in the expertise to a concept in POwl
j )
into an instance in the ontology expressed with the language
OWL/RDF. This transformation is based on a de¯ned tem-
plate (e.g. Ontology.xslt) not showed in this paper. The
result of this step is an XML document called Instance.xml,
describing an instance in the ontology of the data source
being integrated; 2. the second one is the mediator. His
main roles are : a. to create each instance in the document
Instance.xml, returned by the wrapper, in the ontology; b.
to regroup together, for each data type property (of a class)
all its instances in the ontology. This step may be accom-
plished by querying directly the ontology with one of the
languages of ontologies (i.e. DLQuery etc.) or using XQuery
language. This result is stored in an XML document named
GroupInst.xml. c. to deduce similarities (dissimilarities) by
transforming the document GroupInst.xml, using a template
Similarity.xslt (Dissimilarity.xslt) (not shown in this paper).
The result of this step is stored in the Con°icts.xml (a part
of this result is given in Figure 3).
In the following section, we propose an algorithm, imple-
mented at wrapper level, that permits to reconciliate each
concept in an expertise with a concept that is the most sim-
ilar to it and belongs to the peer' POwl
j .