SOAP
SOAP is an XML-based web service protocol that wraps messages in an Envelope/Header/Body structure and supports WSDL contracts and WS-* extensions.
Purpose
It provides strong contracts, transactions, and security extensions for enterprise web services, and it is the classic standard of enterprise integration.
Mechanism
A SOAP message is XML: the root Envelope contains an optional Header (WS-Security/Addressing and the like) and a Body (an RPC call or a document). WSDL defines the service interface, and SOAP travels over HTTP.
Use cases
- Enterprise system integration
- Payment gateway APIs
- Legacy web services