In practical business terms, Web Services have emerged as a powerful mechanism for integrating disparate IT systems and assets. They work using widely accepted technologies and are governed by commonly adopted standards. Web Services can be adopted incrementally with little risk and at low cost. Today, enterprises use Web Services for point-to-point application integration, to reuse existing IT assets, and to securely connect to business partners or customers. Independent Software Vendors (ISVs) embed Web Services functionality in their software products so they are easier to deploy.

From a historical perspective, Web Services represent the convergence between the service-oriented architecture (SOA) and the Web. SOAs have evolved over the last 10 years to support high performance, scalability, reliability, and availability. To achieve the best performance, applications are designed as services that run on a cluster of centralized application servers. A service is an application that can be accessed through a programmable interface. In the past, clients accessed these services using a tightly coupled, distributed computing protocol, such as DCOM, CORBA, or RMI. While these protocols are very effective for building a specific application, they limit the flexibility of the system. The tight coupling used in this architecture limits the reusability of individual services. Each of the protocols is constrained by dependencies on vendor implementations, platforms, languages, or data encoding schemes that severely limit interoperability. And none of these protocols operates effectively over the Web.

The Web Services architecture takes all the best features of the service-oriented architecture and combines it with the Web. The Web supports universal communication using loosely coupled connections. Web protocols are completely vendor-, platform-, and language-independent. The resulting effect is an architecture that eliminates the usual constraints of DCOM, CORBA, or RMI. Web Services support Web-based access, easy integration, and service reusability.

As stated earlier, a Web Service is an application or information resource that can be accessed using standard Web protocols. Any type of application can be offered as a Web service. Web Services are applicable to any type of Web environment: Internet, intranet, or extranet. Web Services can support business-to-consumer, business-to-business, department-to-department, or peer-to-peer interactions. A Web Service consumer can be a human user accessing the service through a desktop or wireless browser; it can be an application program; or it can be another Web Service. Web Services support existing security frameworks.