  This paper addresses the problem of classifying web documents using domain
ontology. Our goal is to provide a method for improving the classification of
medical documents by exploiting the MeSH thesaurus (Medical Subject Headings)
which will allow us to generate a new representation based on concepts. This
approach was tested with two well-known data mining algorithms C4.5 and KNN,
and a comparison was made with the usual representation using stems. The
enrichment of vectors using the concepts and the hyperonyms drawn from the
domain ontology has significantly boosted their representation, something
essential for good classification. The results of our experiments on the
benchmark biomedical collection Ohsumed confirm the importance of the approach
by a very significant improvement in the performance of the ontology-based
classification compared to the classical representation (Stems) by 30%.
