Web Services Concepts

So what's new about Web Services that makes them different? Well, these services are defined on a set of industry-based standards, which must be conformed to by any vendor in order to make it an approved Web Service. Also, these services use the XML language and the HTTP protocol.

Furthermore, the knowledge required to develop such applications is not uncommon and therefore its development will not involve the expenses of extensive training and using the "trial and error" approach.

Now that you have a fair idea of what Web Services are, the next section will detail the architecture and components of Web Services, first describing the requirements for talking across different hardware and software components. Figure 22.1 represents the architecture of Web Services.

Figure 22.1. Architecture of Web Services.

As you can see in the figure, the following components are needed:

• A method to communicate and interoperate seamlessly between different systems/applications

• A service through which the services can be described to enable clients to invoke it

• A lookup type service synonymous to a registry service to look up the location of the services, and the methods provided by them, before communicating with them

All these components should be based on a language that provides the flexibility to define data (like the properties of a system) and that can be understood by any application regardless of the platform or system the application resides on.

The languages that fit those component specifications are

• Simple Object Access Protocol (SOAP)

• Web Services Definition Language (WSDL)

• Universal Description, Discovery, and Integration (UDDI)

• eXtensible Markup Language (XML)

The next sections will explore each of these languages in more detail.