To trivialize things a bit, XML is like a generic-purpose HTML.
Where in HTML markups represent hints to the browser about
The WS-* speci?¬?cations
are almost
?¬?nished
142 Hints Toward a Solution
how to render a page, in XML, markups just represent data.
Figure 2-3 shows an example of an XML document.
XML is at the center of many important satellite speci?¬?cations,
such as XML schemas and XML namespaces, which we do not
cover here.
SOAP
The SOAP speci?¬?cation, currently at version 1.2, de?¬?nes what a
web service message should look like and how it can be sent
between two endpoints. SOAP represents everything using XML.
Imagine having a piece of software that performs the sum of two
integer numbers A and B. A SOAP message requesting your software
to perform the sum may look like that shown in Figure 2-4.
It is an XML document that has a root element called envelope.
The area between
and is called the
body of the message, and it contains the data for your software.
The area between
and is called
the SOAP header element, and it??™s the key to SOAP extensibility.
That is one area of the message where the infrastructure can
weave additional information, enriching the communication
with further capabilities.
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