Introduction to Enterprise Application Integration and Web Services



Introduction to Enterprise Application Integration and Web Services

Web Service

A web service is any piece of software that makes it available over the internet and uses a standardized XML messaging system. XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, and then waits for a corresponding XML response. Because all communication is in XML, web services are not tied to any one operating system or programming language Java can talk with Perl; Windows applications can talk with UNIX applications (Banerji 2008).

Web Services are self-contained, modular, distributed, dynamic applications that can be described, published, located, or invoked over the network to create products, processes, and supply chains. These applications can be local, distributed, or Web-based. Web services are built on top of open standards such as TCP/IP, HTTP, Java, HTML, and XML.

Web Services & distributed solutions

Web services are frequently described as the latest incarnation of distributed object technology. This misconception, perpetuated by people from both industry and academia, seriously limits broader acceptance of the true Web services architecture. Although the architects of many distributed and Internet systems have been vocal about the differences between Web services and distributed objects, dispelling the myth that they are closely related appears difficult (Aalst 2008).

The distributed computing world of Web services centers around XML document design. Protocols and addresses are necessary only as glue support technologies for getting the document to the right place in the right manner. In contrast to the simplicity of basic Web services, these XML documents can be extremely rich and complex. For example, a Web services system I worked on for the US Air Force publishes flight plans that can easily be a megabyte or more in size. Encoding these rich documents in XML ensures that they are extensible at predefined places without disrupting existing document consumers.

Types of Web Services

For simple Web services, only simple data types (string, int, and other types) are sent or received as arguments and values that are returned from methods. You must specify the Java class that provides the implementation for the Web service. InfoSphere™ MDM Server for PIM handles generating any WSDL, and creating any WSDD (Web Services Deployment Descriptor) for the deployment of the service (Arkin 2007). For more complex Web services, you provide WSDD to configure the ability to send ...