• SOAP is often thought of as a protocol extension for doing RPC over HTTP.
• This is not completely accurate: SOAP is an XML message format for exchanging structured, typed data.
• It may be used for RPC in client-server applications but is also suitable for messaging systems that follow one-to-many (or publish-subscribe) models.
• SOAP is not a transport protocol. You must attach your message to a transport mechanism like HTTP.