Dinesh,
Messaging styles and message exchange patterns are concepts from
SOAP,
and they're not used in RESTful analysis. Sam will know better than I,
but I'm pretty sure that describing HTTP in terms of the SOAP concepts
gives you document-literal for the messaging style and
request-response for the MEP.
Of course, you can implement other styles and MEPs on top of HTTP
(that's what SOAP does), but in RESTful design your thinking is
oriented around different concepts: resources, representations, etc.
Does this help?