on identified by a uniform resource identifier (URI), whose interfaces and binding are capable of being defined, described and discovered by XML artefacts and which supports direct interactions with other software applications using XML-based messages via Internet-based protocols. Web services make software/services/service enablers/business processes accessible to any service provider to support activities in a process. Web services are the tools that enable businesses to quickly and effectively integrate internal systems and share information and logic across the enterprise. A client is software that makes use of a web service, acting as its 'user' or 'customer'. A message is the basic unit of communication between a web service and a client; data be communicated to or from a web service as a single logical transmission. In order to make use of a web service, it is necessary to know what information is expected and in what form. Therefore, the interface needs to be explained for use by remote parties. The structure of the messages accepted and/or generated needs to be described. An example can be seen in Figure A1.2. A number of services are defined in the web and by the different service providers and enterprises. For a specific application own services as well as services belonging to service providers may be used. Those services may use other services in other domains. For example a billing service may need infor- mation about the user account or his/her credit card transactions. All these services need to communicate and understand each other in order to provide a certain application with specific tasks. Businesses/operators that purchase this type of service are expecting to realize benefits along the lines of shorter payback periods, higher return on investment (ROI) and a freeing of staff to manage projects they deem more strategic to the competitiveness of their business. The basic architecture model includes web services technologies capable of: Exchanging messages/requests Describing the web services 