A unified framework based on Petri-net for the modeling of service behavior and QoS is proposed. Based on this framework a set of service consistency rules are derived to improve the accuracy of service discovery and to ensure the system consistency in service substitution. A middleware named SOBECA (service-oriented, behavior and capability support architecture) compatible with current Web services standards is developed to make a proof of concept of the framework. In SOBECA the service description is extended with behavior and quality attributes which can be automatically checked against current requirements.