Web Services technology for interoperability, dynamic discovery and integration of distributed components is to be applied in various environments, such as networks of relatively narrow and unstable wireless connections. However, in such environments it is necessary to deal with resource limitation. Our work adopts mobile agent technology in response to this problem and presents a mobile agent framework for Web Services integration. This framework utilizes BPEL (Business Process Execution Language for Web Services) for description of the integration logic, and provides declarative descriptions for physical behaviors (migration and cloning). This facilitates addition or change of physical behaviors according to the environmental conditions while preserving the integration logic. This paper especially focuses on formal definition and discussion of our framework.