B2B Integration : A Practical Guide to Collaborative E-commerce

XML Standards for E-business 205
7.6. Simple Object Access Protocol (SOAP)
In order to accomplish B2Bi over the Internet, applications of multiple
trading partners have to communicate. In the past, this was accomplished
using distributed component architecture such as CORBA and DCOM.
However, such architecture does not leverage the Internet, as it is based
on remote procedure calls (RPCs), which can cause a substantial security
threat over the Internet and usually the corporate firewalls and proxy
servers block such traffic.
SOAP is ideal for B2B applications, since it is an XML-based
protocol for exchange of information over the Internet in a decentralized,
distributed environment.
It consists of three parts: an envelope that defines a framework for
describing what is in a message and how to process it, a set of encoding
rules for expressing instances of application-defined datatypes and a
convention for representing remote procedure calls and responses.
7.6.1. SOAP messages
All SOAP messages are encoded using XML. The SOAP message,
essentially an XML document, contains the following XML elements
(see Figure 7.10):
• A SOAP envelope, which is the top element of the XML document
and defines the contents of the message.
• A SOAP header that contains header information. This element is
optional. The header is a generic mechanism for adding features such
Figure 7.10. — Components of a SOAP message