Simple Object Access Protocol

High-level communication protocol
- Mostly: request/reply semantics (RPC style), also documents (message passing) …
SOAP defines message formats, not the protocol as such
Relies on the HTTP for actual delivery
Details
- Using a common representation of data (XML)
- Use a generally available transport protocol: mostly HTTP
- E.g., to traverse firewalls
- Implementations using other protocols (e.g., SMTP) exist!
- Comment: W3C defines the use of SOAP with XML as payload and HTTP as transport

Envelope (mandatory)
- Top element of the XML document representing the message
Header (optional)
- Determines how a recipient of a SOAP message should process the message
- Adds features to the SOAP message such as authentication, transaction management, payment, message routes, etc…
Body (mandatory)
- Exchanges information intended for the recipient of the message
- Typical use is for RPC calls and error reporting