What is the meaning of Web Services?

WEB SERVICES:-

    Web Service are consist of two basic elements that are:-

• XML
• HTTP

   Extensible Markup Language (XML):-
               XML is a markup language and it is a set of rules that use for encoding a document in the format of both human readable and machine readable.XML provides a language which can be used between different platforms and programming languages and still express complex messages and functions.XML is designed is to store and transfer data.XML is much like HTML language. In this language tags are not predefined,user have to create their own tags.XML is w3c recommended.If anyone say that XML is a replacement to HTML language then it is absolutely wrong.XML is not a replacement to the HTML language because XML is designed to transfer the data and HTML is used to format and display the data.
                           There are Schema and validation in XML language  it contains a reference to a Document Type Definition (DTD), and that its elements and attributes are declared in that DTD and follow the grammatical rules for them that the DTD specifies. 

SCHEMA:-     
          The schema of the XML language are Document Type definition and XML Schema.
Document Type Definition is the oldest schema language and XML schema is the newer language described by the w3c.

Hyper Text Transfer Protocol(HTTP):-
           Hyper Text Transfer Protocol(HTTP) is used as command or a command defines how message are formatted and transmit and in the response what web servers and browsers take actions.To understand it we can take this example that when an URl is entered in browser it sends a HTTP command to the web server to check it and direct to the requested webpage.HTTP is multi-linear sets of objects that build a network by the use of logical links that are known as hyperlinks between some text.HTTP is a protocol to transfer the hypertext.
           HTTP function as a request-response protocol.When the client submit the HTTP request message to the server, the server provides the resources in the form of HTML files.