Service design Philosophies are :

SOAP : It relies on XML Information Set for its message format, and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) or Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission. It is transfer neutral Commonly used in a scenario where you have a more controlled environment.

<soap:Envelope xmlns:soap="...">
<soap:Header>
<!-- additional xml based headers
securit, rm, tx -->
</soap:Header>
<soap:Body>
 <Invoice>.. </Invoice>
</soap:Body>
</soap:Envelope>

REST:  REST don’t attempt to achieve transport neutrality but, RESTful services typically embrace HTTP, the “Web” transport. In REST, services are modeled as an “resources” and they are given an unique identifier (URI). They are communicated via a standard service contract (GET, POST,PUT,DELETE,HEAD). Resources can be represented as XML,RSS,JSON,etc. Commonly used in public facing web-service scenarios.