In the context of the valorization of Tunisian patrimony, we propose an approach to represent semantic properties on contents: heterogeneous information (multimedia) concerning patrimony objects. We develop indexing and information retrieval (IR) processes based on noun phrase (NP) and its semantic representation. These processes use natural language processing (NLP) to take into account the NPs structure organization. In view of this study, the ontology has been proposed to capitalize the concept of knowledge as NP and its semantic relations.