  Within the documentary system domain, the integration of thesauri for
indexing and retrieval information steps is usual. In libraries, documents own
rich descriptive information made by librarians, under descriptive notice based
on Rameau thesaurus. We exploit two kinds of information in order to create a
first semantic structure. A step of conceptualization allows us to define the
various modules used to automatically build the semantic structure of the
indexation work. Our current work focuses on an approach that aims to define an
ontology based on a thesaurus. We hope to integrate new knowledge
characterizing the territory of our structure (adding "toponyms" and links
between concepts) thanks to a geographic information system (GIS).
