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WS-Policy is a specification that allows web services to use XML to advertise their policies (on security, quality of service, etc.) and for web service consumers to specify their policy requirements.

WS-Policy is a W3C recommendation as of September 2007.

WS-Policy represents a set of specifications that describe the capabilities and constraints of the security (and other business) policies on intermediaries and end points (for example, required security tokens, supported encryption algorithms, and privacy rules) and how to associate policies with services and end points.

Policy Assertion[edit]

Assertions can either be requirements put upon a web service or an advertisement of the policies of a web service.

Operator tags[edit]

Two "operators" (XML tags) are used to make statements about policy combinations:

  • wsp:ExactlyOne - asserts that only one child node must be satisfied.
  • wsp:All - asserts that all child nodes must be satisfied.

Logically, an empty wsp:All tag makes no assertions.

Policy Intersection[edit]

The policy intersection is a semantic (as opposed to syntactic) intersection of two policies. The intersection is a new policy that complies with both their requirements/capabilities - or, if the policies are incompatible, this is discovered by both parties.

Often synonymous assertions are considered incompatible by a policy intersection. This can easily be explained by the fact that policy intersection is a syntactic approach, which does not incorporate semantics of the assertions. Furthermore it ignores the assertions parameters. Opposed to what the name might suggest, it is (although quite similar) not a set-intersection.

Associated specifications[edit]

External links[edit]