Summary

It is important to have a solid understanding of how to architect Web services before you start building them. This means having a clear picture of how the logical and communication architectures work together to provide the functionality necessary for Web services (see Figure 2-18). Unlike some architecture models, this is not simply an architecture of convenience, but rather an architecture of necessity. Any process exposed as a Web service must have an interface layer that allows consumers to interact with it. Likewise, any application that consumes Web services must have an integration layer. Together, these layers fulfill the communication architecture.

Figure 2-18: Combined logical and communication architecture for a Web services call

In our illustrations and examples, we have focused on applications in which different owners provide the service and consumer. Does this architecture change if its owner is the only consumer of the service? Since this is a logical architecture, the answer is no. The same functions and processes have to be provided regardless of the identities of the consumer and end user. However, in implementation, some things might be done differently if the service and consumer had the same owner. We will look at this scenario in our sample applications in Chapter 8.

The next question might be whether it makes sense for an organization to expose their services as a Web service. This must be answered on a case-by-case basis. For example, in our computer manufacturing process, it might make sense for the video card manufacturer to sell its product directly to consumers. It would require some work on packaging and probably enhancing the company's customer service, but it could certainly be feasible. However, under very few scenarios does it make a lot of sense for a smaller organization to expose a process as a Web service if it will be the only organization using it. That would be like the video card manufacturer using resources on the packaging for its video cards and then purchasing every card made. In fact, if the company cannot get enough external consumers to purchase its video cards, a benefit will likely not be realized because the market reuse won't be there to justify the design and development effort. Likewise, whatever application architecture is being utilized in an organization will continue to serve as the best solution in many instances.

In the next chapter we will take a brief look into some of the newer technologies needed to implement Web services. An understanding of these will be key to knowing when and how to use them in our implementations.