We propose a top-down design approach which specify desired global behaviors with a conversation protocol,after we analyzed the drawback of the bottom-up approach,and then verify whether the global protocol satisfy the preset system goals.

On the basis of analysis of features of Web service,this paper takes the example of BPEL4WS language to introduce the conversation protocol based on colored Petri net and corresponding method for Web composition service designing.

The notion of conversations,and their associated conversation protocols,as abstract representations to be used to characterize interaction between agents has been discussed in the agent community for several years now.