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Re: WSFL question

From: Francisco Curbera <curbera@us.ibm.com>
Date: Wed, 23 May 2001 13:39:40 -0400
To: www-ws@w3.org
Message-ID: <OF05BF3FDC.672E3B96-ON85256A55.0060FD23@pok.ibm.com>


You are quite right.

First, there is a certain ambiguity at the WSDL level, with respect to the
possibility of having multiple ports inside a service. They can be
different bindings of the same portType or different portTypes. The result
is a wide variety of possible combinations which is not easy to treat in a
uniform way. I would like to see this clarified at the WSDL level first;
WSFL decided to stay away from trying to propose a solution to the problem,
and I think that is the right thing to do.

On the other hand, while it is true that WSFL defines models at a higher
level, WSFL is also concerned with providing binding information which is
complete and useful. Because of the WSDL issue above, WSFL may not provide
complete information in all cases (so here is room for your middleware to
do something useful, like picking the right binding for a portType when
several options are available). Note also that UDDI locators allow you to
specify a UDDI query that can in fact constrain the type of bindings you
get for your ports.


Omar Benjelloun <omar.benjelloun@inria.fr> on 05/23/2001 12:00:10 PM

Please respond to omar.benjelloun@inria.fr

To:   Francisco Curbera/Watson/IBM@IBMUS
cc:   www-ws@w3.org
Subject:  Re: WSFL question

Thanks for your prompt answer, Francisco.

Still, it's a bit unclear to me. Suppose a service provides two ports
for each of its port types, one that is bound to SOAP, and another one
that uses HTTP/GET, for example. Can I express the fact that I prefer
to use the SOAP ports ? Can I declaratively define a fallback
mechanism between the two protocols ?

I understand that this is rather "low level" compared to the rest of
the spec, and maybe it should be specified sowhere else, but I think a
WSFL+WDSL(+WSEL?) description is all that should be needed to
instantiate a running workflow involving multiple services. Please
correct me if I'm wrong.

Thanks for your help,


Francisco Curbera writes:
 > Omar
 > In WSFL you don't bind individual ports, but complete services. The
 > element allows you to specify how to select a service to bind to a
 > provider. Note that service providers are typed by service provider
 > which are nothing but sets of portTypes. Hence, when you bind the
 > provider to a service you are also binding each portType in the service
 > provider type to a port in the selected service. Note that there is an
 > exception to this model, namely, activities that are dynamically bound
 > based on received data using mobility locators.
 > Hope this helps,
 > Francisco
 > Omar Benjelloun <omar.benjelloun@inria.fr>@w3.org on 05/23/2001 11:09:43
 > Please respond to omar.benjelloun@inria.fr
 > Sent by:  www-ws-request@w3.org
 > To:   www-ws@w3.org
 > cc:
 > Subject:  WSFL question
 > Hi,
 > I have a question regarding the WSFL specification, I hope this is
 > the right place to ask. It is unclear to me how to specify a particular
 > binding/port to use for an activity.
 > Static locators have a service attribute, but as far as I understand,
 > this field references a "service", which may be composed of several
 > ports, possibly for the same port type.
 > On the activity side, only abstract operations and port types are
 > described.
 > So, is there some other place to say which port I want to use for a
 > service ? Otherwhise, how can the workflow engine choose between the
 > different ports that may be offered by a service for the same port
 > type ?
 > Best regards,
 > Omar
Received on Wednesday, 23 May 2001 13:40:21 UTC

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