This paper presents requirements for workflow management systems supporting CITIS. We propose an architecture of global workflow management system which aims at supporting external workflow among different organizations rather than internal one. The architecture consists of five key elements, that is process definition language, process graphic design tool, control engine, status monitoring tool, and interface models. For each of these elements, implementation requirements are presented and its major functions are described. A key concept to the CITIS standard is the integration of disparate systems in distributed environment. This leads us to place a special emphasis on the interface models that can enhance the interoperability between externally participating workflow systems. Two interface models for the global workflow management system are explained. CORBA, the most widely accepted standard for distributed object management, can be adopted to facilitate the integration. World Wide Web can be used for the underlying platform on which information is exchanged and the status of processes instances is monitored. The workflow management system can provide a ready and easy access to and management of the data for CALS environments.