Chapter 3 - Web Services

Abstract

Web Services are platform-independent and language-independent, because they use standard XML languages. This means that the client program can be developed in C++ and running under Windows, while the Web service is programmed in Java and running under Linux. Most Web Services use HyperText Transfer Protocol (HTTP) for transmitting messages (such as the service request and response). One of the oft-cited advantages of Web Services is the fact that they lend themselves naturally to build loosely coupled systems. These types of systems are more scalable than strongly coupled systems, and impose fewer architectural requirements on the actual implementation of the Web services. Web services also have some disadvantages: (1) Transmitting all the data in XML is obviously not as efficient as using a proprietary binary code, (2) Web Services are relatively new and, although the core specifications that deal with fundamental languages (XML, WSDL, …) and protocols (HTTP, SOAP, …) are pretty stable, the world of Web Services is still evolving at a fast pace. Standards dealing with more advanced capabilities expected from distributed systems, such as transactions and security, are either very new or still in the works. SOAP and WSDL are essential parts of the Web Services Architecture. Despite having a lot of protocols and languages floating around, Web Services programmers usually only have to concentrate on writing code in their favorite programming language and, in some cases, in writing WSDL (Web Services Description Language). SOAP code, on the other hand, is always generated and interpreted automatically.