What is Web services in simple terms

Question

I am little bit confused about what really a web service is. You say Amazone web services,etc like that, they offer information. So what is the requirement to be a web url to be a web service ? Let's say I am not much familiar with web development, how could you explain it to me ? But I can get it if you point some ways. And also little about SOAP and REST basically for someone really new

Answer 1

Duplicate: http://stackoverflow.com/questions/226108/what-is-a-web-service-in-plain-english

REST and SOAP duplicate: http://stackoverflow.com/questions/209905/rest-and-soap

Answer 2

The W3C defines a Web Service as (quoting) :

A Web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP-messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.

That definition is maybe a bit too restrictive, considering how that term is used nowadays -- I'd probably go with just the first part of that definition, which is quite generalist :

A Web service is a software system designed to support interoperable machine-to-machine interaction over a network.

Wikipedia also has some interesting definitions, like :

In common usage the term refers to clients and servers that communicate over the Hypertext Transfer Protocol (HTTP) protocol used on the Web.

From what I've seen :

• A couple of years ago, when we said "web service", we generally meant "SOAP, WSDL, ..."
• Now, when we say "web service", we often mean "whatever allows to call something on another server, be it SOAP, REST, ..."

Answer 3

What is a web service

It is many things. In programming, in generally refers to a web page, that can be called from an application (be it another web page, or desktop app), and the caller will pass in data to it, or receive data from it.

In this sense, it's basically like a 'method' or 'function' in a normal programming language; except you're calling it over the internet.

SOAP

A message format. As discussed above, a web service is a basically a 'method' or 'function'. SOAP is the 'instructions' and 'data' to this method. It will outline data types, and possibly a bunch of data as well. It is an XML format.

REST

REST is the means of implementing an interface to your application but, implementing access control, and other such things, specifically with HTTP Response codes. So you will get a 401: Denied (I think that's the right code), if you don't have access. There are other types of response codes that are useful. It also makes use of other HTTP commands like PUT/HEAD/OPTIONS.