Several major collaborative modeling prototype systems are briefly discussed here. CSM  is a webbased collaborative modeling system. Within its clientserver architecture, the server contains a global model, while every client owns a local copy of this model. When a user has locally modified the model, it is propagated to all of the other users through the server. However, concurrence is managed by a strict token passing manner, which turns the clients into several independent modeling systems just using the same product model alternatively.
WebSPIFF  is also a web-based collaborative modeling system. It adopts the so-called thin client mode of client-server architecture. In WebSPIFF, the server does operations related to solid modeling, and the client mainly deals with user interface operations and result display. Connection between the client and server is done by direct socket. When updating the client user interfaces, images used to update client user interface are stored in the SPIFF server, and the server notifies the clients to download them through the hypertext transfer protocol. However, this approach increases the data exchange times on the network, and the time delay to update the client user interface. When user frequently operates on the product mode, the client user interface could not be updated in time.
CADDAC  employs a three-tier architecture that partitions the collaborative design system into a server-tier, a client-tier and a database. In CADDAC, the server controls a central model and does most modeling operations. The client is thin in that it needs to have only a connection to the server and graphics libraries for 3-D display. Also, the system is capable of doing collaborative constraints management. Introducing Web Service to ULA based multidisciplinary collaborative product design has received extensive research in recent years [8,9,10,1 1]. The research focus of this paper is based on the above work, and presents a Web Service and ULA based approach in distributed M&S environment to support complex and multidisciplinary product design.
A case study
In this chapter, a prototype Web Service-based system of locomotive collaborative design based on distributed network is presented. The design of locomotive multidisciplinary dynamics system depends on three domain models principally: control model, mechanical model and the hydraulic servo model. We realized that the multidisciplinary modeling and simulation of locomotive development in a Web Service distributed environment. The 3 domain modeling systems were implemented by ADAMS (mechanical system), M\ATLAB (control system) and Hopsan (hydraulic servo system). The interaction among various domain models based on Web Service distributed environment is shown in Fig. 6. The collaborative simulation process can be controlled by the session manager, and the view browser g