Web - (Web Service|Webservice)

A Web service is a set of functions packaged into a single application programming interfaces (API) that is available to other systems on a network.

The term generally refers to clients (consumer) and servers (provider) that communicate over the HTTP protocol used on the Web. Basically, you can compare the web service logical as a web form process. When you click on the button (ok, send, apply, …) of a web form, you send the data present in the form and the server send you back other data.

The web service process is the same, you send an HTTP request to a server that send you back the result not in an HTML format but in a XML or JSON format.

It's why :

• when you code a program, you have to define the URL of the Web Service.
• when you see the log session of the web service server, you can see the name of a browser (because the web service implementation simulate a browser)

The W3C Web service is a key concept of a soa architecture. Application interoperability is the goal of Web services.

For example, a banking Web service may implement functions to:

• check an account,
• print a statement,
• and deposit and withdraw funds.

Such services tend to fall into:

• SAOP Web Services Web Service - Simple Object Access Protocol (SOAP)
• RESTful Web Services. Web Service - Representational State Transfer (REST|RESTful) Web services
• GraphQL : GraphQL

Other approaches with nearly the same functionality as web services are:

• Object Management Group's (OMG)
• Common Object Request Broker Architecture (CORBA),
• Microsoft's Distributed Component Object Model (DCOM)
• or SUN's Java/Remote Method Invocation (RMI).

• Web Services: Promises and Compromises
• Web_service
• Oracle® Fusion Middleware Introducing Web Services 11g Release 1 (11.1.1.5) Part Number E14294-05
• Eclipse - WTP - Web services overview