| Although not specifically part of the J2EE specification, Web services support is now a prominent feature set of the WAS V5 product. We found that the WAS help documentation (InfoCenter) provides a concise description of what Web services are: -
Web services are self-contained, modular applications that you can describe, publish, locate, and invoke over a network. -
Web services could be weather reports or stock quotes. Transaction Web services supporting business-to-business (B2B) or business-to-client (B2C) operations could be airline reservations or purchase orders. -
Web services reflect a new, service-oriented approach to programming, based on the idea of building applications by discovering and implementing network-available services or by invoking available applications to accomplish some task. This service-oriented approach is independent of specific programming languages or operating systems. Instead, Web services rely on pre-existing transport technologies such as HTTP and standard data encoding techniques, such as XML, for invoking the implementation. -
The key components of a Web service are as follows : -
Simple Object Access Protocol (SOAP) -
Web Services Description Language (WSDL) -
Universal Discovery, Description, and Integration Protocol (UDDI) Looking at this description, it is hard to see what is so new and revolutionary. After all, there are many mechanisms for invoking "services" over a network ”for example, J2EE provided mechanisms such as servlets and EJBs or traditional distributed system protocols such as RPC and CORBA, and so on. What is new about Web services lies more in how they are defined and implemented: They can be implemented across many programming languages; they are designed to be self-describing ; and they are evocable over the open Internet. SOAP is the basic protocol for communication among Web services. It can be characterized as a remote procedure call (RPC) protocol over HTTP (although not restricted to HTTP alone). The fact that it's an RPC enabled over the open Internet is what's new. WSDL defines how a Web service is cataloged and described so that it can be discovered and invoked by another program (Web service). UDDI serves as the directory for Web services, allowing the WSDL to be queried in an open fashion. What's new? It's the ability to discover and invoke Web services programmatically across the open Internet. Underlying all of the protocols is XML, which is used as the data format language. A program that can parse and create XML can operate on any of the Web service protocols. Beyond the basic set of Web service protocols, SOAP, WSDL, and UDDI, there are other protocols in various stages of definition and standards body ratification, which will extend the ways with which an application designer can make use of Web services. WAS V5 provides implementations of some of these newer protocols as well, such as Web Services Invocation Framework (WSIF) and WS-Security. The Domino platform is not excluded from the Web service initiatives. It is easy to see various ways in which Domino functions can play in the Web services arena. Native Domino functions such as document handling, workflow, directory, and e-mail can be opened as Web services. Application functions developed on a Domino base can be made available as Web services ”we will see how it is possible to provide Web services even via LotusScript. All of this gives the application designer more tools with which to construct a Web service-based application. |
