Web Service essay 1

Web Service.
1 Why does the Web Service appear?
Nowadays, the Internet is developing very rapidly. Its former framework is "people to obtain resources on the network, such as programs and documents ". That is to say, the current Web is centered on people to send various requests. Its development trend is that the main body changes from "people" to "programs", such as media players and browsers, that is, the "Application-centric" Web. In fact, before the emergence of Web Services, people were already doing this, such as Java Servlet and CGI, but different program systems adopt different data definitions, therefore, the interaction between these systems becomes very complex. The emergence of Web Service is to solve the format of communication between different applications.
2. How does the Web Service communicate?
XML communication involves several different methods, such as XML Remote Procedure CALS (XML-RPC), SOAP, or http get/POST.
3. Web Service attributes.
Web Service is any available Service on the Internet. It is implemented through standardized XML communication (XML Messaging) and does not depend on any platform or any programming language.
Although not mandatory, Web Service may have two other attributes:
A) self-describing. if you write A Web Service, you should publish the public interface of the Web Service, at least one document based on natural language. In this way, other developers can easily integrate your services.
B) discoverable. Other programs related to your Web Service (which may be scattered or a centralized system) can find it.
4. Web Service Architecture
The Web Service has two architectures: one is to discuss each function role (role) of the Web Service, and the other is to discuss the protocol layer (protocol stack) of the Web Service ).
For the former, Web Service has three roles: Service provider, Service requestor, and Service registrar. The service requestor obtains the service provider from the service registry and then sends a request to the service provider to provide the service.
For the latter, the Web Service has four layers: Service transport, XML messaging, and Service description) and Service discovery layer ).