Objective
Web Services are open standards (XML, SOAP, HTTP, and so on) that Web applications are designed to interact with for other Web applications.
Web Services can convert your existing applications into Web applications.
In this series of guides, you will learn what Web Services are, why, and how to use them. This series of guides will be useful to those who are interested in learning the basics of Web Services and implementing them in practice.
This is a basic tutorial on the concept of Web Services and does not require the reader to have prior knowledge of these technologies, but it is certainly easier to read if you have a basic understanding of the concepts of XML, HTTP, TCP/IP, and so on.
Defined
Many different books, or different organizations, provide different definitions for Web Services. Some of these definitions are listed below.
- A Web service is any software that enables itself to be accessed over the Internet and using a standardized XML messaging system. XML is used to encode all communications to and from the 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 communications are XML-based, Web service is not bound to a specific operating system or programming language--java can interact with Perl, and Windows applications can interact with Unix applications.
- Web Service is a standalone, modular, distributed, dynamic application that can be described, published, positioned, or created through a network to create products, processes, and supply chains. These applications can be localized, distributed, or Web-based. Web Service is built on open standards such as TCP/IP, HTTP, Java, HTML, and XML.
- Web Service is an XML-based information Exchange system that uses the Internet for direct application-to-application interaction. Such a system can contain programs, objects, messages, or documents.
- A Web service is a collection of open protocols and standards that are used to exchange data between applications or systems. Software applications that are written in different languages and run on different platforms can use Web service to interact with data over a computer network, just like interprocess communication on a single computer. This interoperability (for example, between Java and Python, or between Windows and Linux applications) is attributed to the use of open standards.
As a summary, a complete Web service is any service that meets the following criteria:
- Access via Internet or private (intranet) network
- Use a standardized XML messaging system
- Not tied to any operating system or programming language
- The self-descriptive nature of a common XML syntax
- Accessibility through a simple discovery mechanism
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