Web service composition is a low cost and efficient way to leverage the existing resource and implementation. In current Web service composition implementations

the issue of how to define the role for a new composite Web service has been little addressed. Adjusting the access control policy for a new composite Web service always causes substantial administration overhead from the security administrator. Furthermore

the distributed nature of Web service based applications makes traditional role mining methods obsolete. In this paper

we analyze the minimal role mining problem for Web service composition

and prove that this problem is NP-complete. We propose a sub-optimal greedy algorithm based on the analysis of necessary role mapping for interoperation across multiple domains. Simulation shows the effectiveness of our algorithm

and compared to the existing methods

our algorithm has significant performance advantages. We also demonstrate the practical application of our method in a real agent based Web service system. The results show that our method could find the minimal role mapping efficiently.