Given that this is a Web service, many parties collaborate in this development:
The wholesaler builds the service. It connects the service to its inventory management and exposes some or all of it as a Web service.
The resellers build the clients. They add remote request capabilities to their existing inventory management system.
Obviously, in this chapter, you'll play both roles, but it is important to keep in mind that there are at least two parties involved in this development. This impacts several aspects of the project, including—perhaps most importantly—debugging.
Also note that there is no universal client. Most likely each reseller will implement his or her version of the client. Individual implementations may differ ...