W3C's OWL has gained wide acceptance in the agent community and it has already been used in many agent applications which we think syntactically. By taking advantage of OWL's description logic foundation, this paper defines a hybrid description logic language which facilitates the use of ontologies as first class entities in agent communication. Using this language, we axiomatize cooperative agent behavior. Then we suggest an operational model to implement this behavior. As a case study, we present an application from software package management domain that tests the model's usability.