This paper stresses the importance of establishing a collaborative working context as the basis for design integration. Within a virtual studio environment framework, a hybrid architecture for design tool integration is presented. Each design tool is wrapped as an autonomous service provider with its own data store, thus the project design data is  physically distributed with the design tools. A global product model, which is augmented with meta-data description, is employed to provide a common vocabulary for communications and to assist the management of the distributed resources and activities. Collaboration-aware information is modelled and structured through the meta-data model anda tool model. Based on this, mechanisms for tool service coodination in varying modes are developed. It is then  illustrated, through an implemented prototype system, how the integrated design tools might be used in human design work.