Service Oriented Architectures (SOA) defines systems that allow the linking of resources on demand. SOA resources are available in the network as independent services. This provides a more flexible loose coupling of resources than in traditional systems architectures. Web service technology is nowadays the most well-known connection technology for implementing SOA. Web services allow loosely coupled interaction between services implemented by different vendors. This is possible because the interface provided by web services is defined in terms of an XML-based language called WSDL. Today, Business to Business (B2B) relationships are one of the most important areas for companies.