Regular readers of this column might notice that I've spent a lot of time on WSDL. There's a reason for this: after XML and SOAP, I firmly believe that service description is the most important component of designing, building, and deploying heterogeneous web services.
There are a couple of reasons why this is true. First, it is a precise description of what the bits on the wire will be. Without that, it is exceedingly difficult for distributed applications to talk to each other. It's still possible, and great things can be made — SAMBA is a tour de force of reverse engineering — but that's not really how you want your customers, partners, or colleagues to be spending their development time.
Second, if you have the luxury of time and resources — not to mention the managerial foresight — to be able to first design your network interfaces before developing the code behind them, then the service description will be the first thing you will write. The phrase "contract-first" seems to be increasingly bandied about as the official jargon to use here.
