Database Reference
In-Depth Information
Authority
W3C
Primarily addresses Composability, Loose Coupling, and Abstraction
Latest release
Most importantly, when compared with human-readable SLAs, these conditions are ex-
pressed in a machine-readable form. In fact, this specification has a lot of common fea-
tures with the metadata exchange standard, but it's far wider as it expresses service re-
quirements and preferences regarding all other
WS-*
specifications in a detachable form,
presented as an XML policy file. This separation allows you to centralize all policies and
present them in a hierarchical way, simplifying attachment to the provider's WSDL.
Some delivery assurance elements along with their descriptions are as follows:
Element
Description
AtMostOnce
Messages are delivered at most once, without duplication. It is possible that some messages may not be delivered at all.
AtLeastOnce
Every message is delivered at least once. It is possible that some messages are delivered more than once.
ExactlyOnce
Every message is delivered exactly once, without duplication.
Messages are delivered in the order that they were sent. This delivery assurance can be combined with one of the preceding
three assurances.
InOrder
The
WS-Policy
delivery assurance elements are typically used together with other
WS-
*
specifications for enforcing certain operational requirements, such as reliable messaging
timeout and acknowledgement interval, as shown in the next code snippet.
The following code will help us understand how the policy is defined as a child element
of the
wsdl:definitions
element:
<wsp:Policy wsu:Id="RMAcknowledge_policy">
<wsp:ExactlyOne>
<wsp:All>
<wsaw:UsingAddressing/>
<wsrm:RMAssertion>
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