Difference between REST and WebServices

Question

What is difference between REST and WebService (SOAP), I looked at the facebook api, they use HTTP headers and some parameters (probably xml or non) and return result in xml

Answer 1

For me a service implemented using a RESTful approach wins over one that uses SOAP or RPC in terms of its accessibility. In a relatively closed system where tooling is available to generate stubs and ties based on a WSDL, this is not terribly important. However, if you want to create services that are accessible and available to a wide range of clients, then the uniformity of REST services and ease with which they can be consumed is a big plus i.e. you don't need a heavy RPC stack, just the ability to make HTTP requests.

Not sure this totally answers your question, but if, as you say, you have a system that works based on SOAP (and you control the client and server) then I don't see any reason to change. Besides, some services will naturally lend themselves more to RPC based access, in which case a SOAP interface will be more appropriate.

In terms of performance, one or more layers would effectively be removed from the client and server technology stacks if you don't use SOAP, so all other things being equal, a service which exposes a RESTful interface will win there.