Re: WS-Policy and SAWSDL

Hi Bijan, 

personally, I would say the difference between SAWSDL and Policy is
this: SAWSDL gives information about what the annotated WSDL does, on a
higher level than the name of the interface. Policy gives information
about how (and under what conditions) it does it, assuming the client
already knows what it does.

SAWSDL annotations are meant to help the client (human or automaton)
find the service that Does What The Client Wants(tm). 

Policy is meant to help the client that already knows a service (or a
set of them) to check that the service can do it the way the client
wants.

If the client wants to get current stock information, it wouldn't use
Policy to select from among billing, shipping, weather and stock
services - here's where it would use SAWSDL.

If the client has a number of stock information services, it will use
policies to select the one that will give most up-to-date (QoS)
information for acceptable price, over an encrypted channel. SAWSDL
wouldn't help here.

BTW, both tasks above fall under matchmaking as various people would
define it, yet still I see them as two different tasks.

That's what I call difference of intent. Of course the nature of
semantic annotations and policy assertions is that nobody wants to
constrain them, but the tools people are likely to build with SAWSDL or
WS-Policy will, by market forces, only do some tasks with the
information. One can use Policy as a framework for a programming
language, yet nobody will build a commercial system around that (as far
as I can foresee).

It is possible that in the future the industry will stop being afraid of
semantics and automation, and semantics people will start caring about
QoS parameters, and that QNames and URIs will be reconciled (haha), and
a single unified framework for both policies and semantic annotations
will be created. I won't fight against this, but I don't see the will
currently to go there, yet there is will to have the partial solutions
standardized now.

So from a practical, fairly-short-term point of view, the intentions are
really different. Especially in the Web Services activity, the W3C needs
to have a practical, fairly-short-term point of view, and evolution of
standards is not so expensive. (see
http://www.jacek.cz/blog/archives/000075.html )

Hope this clarifies my position,

Jacek

Received on Wednesday, 13 September 2006 10:09:24 UTC