Web Services

Based on the client-server principle, Web services are software systems that interact with client applications and other services through open Web standards. Consequently, heterogenous computer systems from all over the world can exchange information, regardless of their hardware configurations, operating systems, and software applications. Web services are, therefore, a very popular approach for facilitating automated intra-organizational and inter-organizational communication. This chapter provides a thorough introduction to the Web service concept and the different associated standards and technologies, such as Simple Object Access Protocol (SOAP), RESTful interfaces, and Web Services Description Language (WSDL). This chapter particularly provides a comprehensive introduction for two important Web technologies on which most Web services are based: The Hypertext Transfer Protocol (HTTP) and the Extensible Markup Language (XML). Then, the fundamental Web service architectural principles are explained and two common Web service variants are explored in more detail, namely RESTful and SOAP-based Web services. Using these example implementations, this chapter concludes by comparing the two Web service variants in terms of their different application areas.