Web services are a collection of distributed, reusable application components that selectively expose the functionality of business services and make that functionality available to applications through standardized Internet protocols. Web services are building blocks for creating open distributed systems, and allow companies and individuals to quickly and cheaply make their digital assets available worldwide. The key challenge in today's computing and networking world is to integrate diverse computer applications that have been developed independently and run on a variety of software and hardware platforms. Decoupling client and service development enables a given service to be accessed by a variety of client types (such as browser-based clients and wireless clients) that adhere to the standardized web services technologies.
The web services architecture satisfies these requirements:
- Interoperability. An application that uses a web service component need not be aware of the hardware and software platform on which the service runs. A web service can be accessed by different kinds of clients (such as web applications, wireless applications, and other services), as long as they use the standard web services technologies.
- Encapsulation. An application that uses a web service component need not be concerned with details of the component's internal programming.
- Availability. The developer of a web service must have a way to publish it with enough information so that other developers can find the web service and create a client application component capable of using it.
The web services architecture is based on three related standards: SOAP, WSDL, and UDDI. Generally the three-pronged technologies can be described as follows:
- SOAP (Simple Object Access Protocol) defines the mechanism by which a web service is called and how data is returned. SOAP clients can call methods on SOAP services, passing objects in XML format.
- WSDL (Web Service Definition Language) describes the external interface of a web service so that developers can create clients capable of using the service.
- UDDI (Universal Discovery, Description, and Integration) registries contain information about web services, including the location of WSDL files and the location of the running services, so that a wide community of developers can create clients to access the services and incorporate their functionality into applications.
Related technologies to facilitate web services include HTTP, HTML. XML, WML and URL.
- HTTP: The Hypertext Transfer Protocol (HTTP) is an application level protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems. Secure HTTP provides a variety of security mechanisms to HTTP clients and servers, providing the security service options appropriate to the wide range of potential end uses possible for the World-Wide Web (WWW).
- HTML: Hyper-Text Markup Language is a markup language used to contruct web pages for wired devices.
- XML: eXtensible Markup Language is a markup language used to construct web pages .
- WML: Wireless markup language is a markup language based on XML for wireless and mobile web communication.
- URL: URL is the syntax and semantics for a compact string representation of a resource available via the Internet. For example, we use URL to locate web addresses and FTP site addresses.
Web Services and Technologies