ODAC (Open Distributed Applications Construction) provides a modeler with a methodology of distributed applications development in order to enable him/her to describe the system he/she is developing. This description is the specification of the system in UML with ODP semantics. ODAC makes distinction between the specification of the system behavior independently of any execution environment, called the behavioral specification (corresponding to the Platform Independent Model as described in the OMG Model Driven Architecture), and the parametrization of this specification according to a target execution environment in order to transform it into a operational specification. We then provide modelers with a behavioral specification guideline to help them to write their behavioral specifications. We also provide guidelines for the description of execution environments, such as the MASIF-DESIGN guideline for MASIF compliant mobile agent platforms and the ODACforANTS guideline for the active networks. This document focuses on the ODAC guideline for behavioral specifications.