• • We shall present our approach for knowledge Management, based on materialization of organizational memories through organizational semantic webs. Such an approach relies on building and reasoning on ontologies describing the main concepts shared in a domain knowledge.

Such ontologies enable to associate semantic annotations to resources (persons, documents, software, services) constituting the organizational memory. We will analyse the hypotheses underlying this approach and we will study several scientific problems to be solved from ontology and annotation viewpoints: • cooperative building and enrichment of an agreed ontology from human sources or from heterogeneous information sources such as textual documents or databases, • semi-automatic creation of annotations on the organizational sources from heterogeneous sources, • ontology-guided search and ontologuy-guided resource composition, • evolution of the organizational semantic web...

This approach will be illustrated by several scenarios and several concret applications: • project memory for a professional community (illustrated in automotive sector), experiment memory for a scientific community (illustrated by a memory of experiments of biologists), support to cooperative work (illustrated by support to cooperative reasoning in a health network), support to watch (illustrated by watch in building sector), competence management (illustrated by inter-firm skills cartography in the telecommunication domain).