An e-barter system is an e-commerce environment where transactions do not necessarily involve money. They are multi-agent systems where agents perform exchanges of rewources on behlaf of their respective users. Besides, their strucutre is based on a tree of markets. In this paper we show how to develop suitable designs for this kind of systems by means of web services by using WS-BPEL. Since the formal specification abstracts most practical details, the development of such design definition requires to face several challenges. We present two alternative designs that both comply with the formal specification.