Summary

Chapter 9

Discovery Mechanisms for Web Services

One of my main motivations for moving to Colorado several years ago was skiing, and because getting to the nearby ski areas often requires driving over snow-packed mountain passes, I bought an SUV.

It amazes me that the SUV that reliably gets me to my favorite ski areas all winter is assembled from parts mostly made by companies other than the automobile manufacturer. In fact, only about 30 percent of the parts that make up my SUV are manufactured by the automobile manufacturer. For the remaining 70 percent of parts, the automobile manufacturer has built up a vast network of second-tier and third-tier suppliers that feed its just-in-time inventory system.

Web services can provide considerable value to supply chain management (SCM) systems that coordinate transactions such as those between the automobile manufacturer and its suppliers. The automobile manufacturer can advertise via WSDL how it will electronically submit orders to its suppliers and how it expects to receive purchase orders for the goods received.

For example, let's say that a supplier called Fabrikam Wing Nuts needs to obtain the WSDL document from the automobile manufacturer called Contoso Motor Company in order to integrate with Contoso's SCM system. It could make a sales call to Contoso Motor Company and obtain the URI for the WSDL documents and give Contoso the URI where the orders should be sent. Or it could place a telephone call to Contoso to exchange the information.

But wouldn't it be nice if a vendor did not need to have explicit conversations with Contoso in order to learn about the Web services Contoso exposes? Wouldn't it be nice if Contoso could locate your business when it was in desperate need of wing nuts?

Companies need a way to advertise the Web services they support and for clients to discover those services. In this chapter, I discuss two types of discovery mechanisms for Web services: Universal Description, Discovery, and Integration (UDDI) and DISCO. UDDI is a central and hierarchical directory service; DISCO promotes a more free-form browsing model for locating Web services.