To quote from the document's introduction
Web Services Policy 1.5 - Primer is an introductorydescription of the Web Services Policy language. This documentdescribes the policy language features using numerous examples. Theassociated Web Services Policy 1.5 - Framework and Web ServicesPolicy 1.5 - Attachment specifications provide the completenormative description of the Web Services Policy language.
If you are interested in getting a good grasp of the fundamental concepts and ideas behind the WS-Policy language, this document might just be for you!