In my last blog I discussed the rise of a new era in SOA development with the use of Java Web Services technology powered by the implementation of WS-* specifications. Today, I would like to write few lines about policy metadata – the real core of these new technologies.
Policy language and its usage is described in two separate specifications (which have already been submitted for standardization by W3 Consortium):
- Web Services Policy Framework (WS-Policy) specification and
- Web Services Policy Attachment (WS-PolicyAttachment) specification
These two specifications bind all other WS-* specifications together into one complex solution.
The main goal of the WS-Policy specification is to introduce a flexible and extensible way of expressing and understanding the capabilities, requirements and general web service properties. In other words, WS-Policy provides a web services policy language together with domain-neutral rules as to how to process and interpret these policies. To complement the WS-Policy specification – which is strictly focused on defining policy language – WS-PolicyAttachment completes the whole picture by defining the means of attaching actual policy expresions to policy subjects to which these expressions apply. This second specification also describes the way how to use policies in the context of web services description mechanisms – WSDL and UDDI.
WSIT introduces its own policy engine and I am a part of a team working on its design and implementation. We do our best to make sure the implementation is interoperable and – of course – fully compliant with WS-Policy and WS-PolicyAttachment specifications. Currently, we are still in a development phase and there’s much to be tested and polished yet. But we have already achieved success in supporting all main use case scenarios as well as having demonstrated our ability to interoperate with policy engines from other vendors at several Interoperability workshops.