Chapter 10: Core Messaging Example 59
(04) <xop:Include
(05) href="cid:ex.mspress.microsoft.com/ebook.zip"/>
(06) </b:content>
(07) </b:EBookResponse>
(08) </soap:Body>
Line 01 The soap:mustUnderstand attribute is added to the message. When the value of this
attribute is set to 1, the SOAP processor must understand how to process the element or
processing must fail.
Transport Independence
One of the commonly used message transport protocols for Web services is HTTP. However,
numerous other transport protocols are expected and appropriate for use within the Web ser-
vices architecture. Transport protocol selection is a deployment or run-time decision that is
left to system administrators. The transports in use for a given Web service are defined in
WSDL binding elements.
The SOAP specification defines a binding to HTTP for Web services. An example of these
HTTP headers is shown here:
HTTP Message Headers
(01) POST /orders HTTP/1.1
(02) User-Agent: Mozilla/4.0
(03) Content-Type: text/xml; charset=utf-8
(04) SOAPAction: "http://http://ex.mspress.microsoft.com/PO"
(05) Content-Length: 570
(06) Expect: 100-continue
(07) Connection: Keep-Alive
(08) Host: 172.30.177.248:80
Line 01 When using HTTP 1.1, Web services messages use HTTP POST.
Line 03 The HTTP Content-Type is text/xml. As shown in the previous example, SOAP mes-
sages using XOP have a HTTP Content-Type of application/xop+xml.
Line 04 The SOAP action is provided in the HTTP header as a hint to help facilitate message
routing and processing. However, all vital information regarding the intent of a message
is carried in the SOAP Envelope.
Addressing: Using Endpoint References
When the Order message is transmitted from the school's procurement system to the book-
ordering system, message routing and delivery information, such as the endpoint address,
must be provided. This routing and delivery information can be obtained by the sender
through multiple means. One approach is through an out-of-band exchange of Endpoint Ref-
erences between the system administrators.