WS-Policy et. al. This is one of the most appreciated features in the WS-*
cornucopia released over the last months ... it is all about defining policies
for your Web services.
The current implementation in WSE 2.0 (TP) heavily focuses on WS-SecurityPolicy to describe which
security policies are required for communicating with Web services nodes. Aaron Skonnard
provides in his article an overview of WS-Policy and other related
specifications and defines a general framework that can be used and extended by
Web services specifications to describe a broad range of Web services policies.
Check it out on MSDN's XML Web Services Developer Center.
WS-Policy
defines a general framework that can be used and extended by other Web
services specifications to describe a broad range of Web services policies.
WS-Policy defines a policy to be a collection of one or more policy assertions
(see Figure 1).
A policy assertion represents an individual preference, requirement,
capability, or other general characteristic. There are two additional
specifications that define standard sets of policy assertions that can be used
within a policy expression. The Web Services
Policy Assertions Language (WS-PolicyAssertions) specification
defines a set of general message assertions and the Web
Services Security Policy Language (WS-SecurityPolicy)
specification defines a set of common security-related assertions.
WS-Policy provides a flexible and extensible grammar for expressing
policies in a machine-readable XML format. The XML representation of a policy
is referred to as a policy expression. A policy expression is bound to a
policy subject, or in other words, the resource it describes (e.g., a Web
service endpoint). The mechanism for associating a policy expression with one
or more policy subjects is referred to as a policy attachment.
The WS-Policy specification defines the general model and syntax for
policy expressions and policy assertions but stops short of specifying how
policies are located or attached to a Web service. The WS-Policy authors
expected other specifications to address this issue in a variety of ways. The
Web
Services Policy Attachment (WS-PolicyAttachment) specification is
one such specification that defines how to attach policy expressions to XML
elements, WSDL definitions, and UDDI
entries.