Level: Advanced Contributors: IBM, BEA Systems, Microsoft, SAP AG, Sonic Software, VeriSign 01 May 2003
Updated 09 Mar 2006 WS-Policy provides a general purpose model and syntax to describe and communicate the policies of a Web service.
WS-Policy assertions express the capabilities and constraints of a particular Web service. WS-PolicyAttachments defines several methods for associating the WS-Policy expressions with Web services (i.e., WSDL). The specifications have been updated following the
republication of WS-Security Policy in July 2005, to reflect the constraints and capabilities of Web services that are using WS-Security, WSTrust and WS-SecureConversation. WS-ReliableMessaging Policy has also been republished in 2005 to express the capabilities and constraints of Web services implementing WS-ReliableMessaging.
The updated specifications include the definition of nested assertions which allows for additional granularity when expressing certain domain
requirements, i.e., the expression of different algorithm suites for a particular transport binding. These specifications help Web services providers and consumers discover the capabilities and constraints that they share to enable interoperability of these services.
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WS-Policy provides a flexible and extensible grammar for expressing the capabilities, requirements, and general characteristics of entities in an XML Web services-based system. WS-Policy defines a framework and a model for the expression of these properties as policies. Policy expressions allow for both simple declarative assertions as well as more sophisticated conditional assertions.
WS-Policy defines a policy to be a collection of one or more policy assertions. Some assertions specify traditional requirements and capabilities that will ultimately manifest on the wire (for example, authentication scheme, transport protocol selection). Some assertions specify requirements and capabilities that have no wire manifestation yet are critical to proper service selection and usage (for example, privacy policy, QoS characteristics). WS-Policy provides a single policy grammar to allow both kinds of assertions to be reasoned about in a consistent manner.
WS-Policy stops short of specifying how policies are discovered or attached to a Web service. Other specifications are free to define technology-specific mechanisms for associating policy with various entities and resources. Subsequent specifications will provide profiles on WS-Policy usage within other common Web services technologies.
Resources
- You can also read some of the other specifications in the WS-Policy family:
- Domain-specific assertions:
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