Re: [sca-bindings] Relationship between sca binding/service and WSDLservice

[Mike Edwards <mike_edwards@uk.ibm.com>]

Anish,

Well written - thanks.

Following up on these parting points:

Some of the examples of restrictions that do *not*
make sense to me are:
...
2) how many ports a service should contain.
3) whether the generated WSDL contains just one service element or many

I'd like to understand this better -
I don't think I do at the moment.

So, how are the number of ports decided?
 If the number of ports is not fixed by either a) the SCDL itself
or by b) some WSDL that the SCDL points
to, this implies to me that important aspects of the deployment 
configuration of the system are not
being captured in any way by the SCDL and are being determined
somewhere else.  Why is this desirable?

Since the service is a grouping of ports,
I suspect point 3) is related to point 2) - but the relationship of
ports to services in the WSDL is not
arbitrary and carries semantic meaning.  How is this semantic
meaning being captured if it isn't somewhere
in the SCDL (or in WSDL pointed at by the SCDL)?


My concern here is that you can have
in your hands the (deployed) SCDL and any WSDLs it references
and still have no idea what is happening
in the runtime.  This does not seem good either for application
assemblers or for deployers.  Why
is this freedom of approach useful?


Yours,  Mike.

Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
Email:  mike_edwards@uk.ibm.com

Anish Karmarkar <Anish.Karmarkar@oracle.com>

10/07/2008 07:40

To	OASIS Bindings <sca-bindings@lists.oasis-open.org>
cc
Subject	[sca-bindings] Relationship between sca binding/service and WSDL service

Based on the agenda, it looks like I took an action
to send an email 
regd the relationship between sca binding/service and WSDL service. I 
believe this was in the context of issue 11. Here are my thoughts:

In SCA, references are wired to services. Services may have bindings 
specified (default to binding.sca) and may have intents/policies 
specified. References may have intents/policies specified.

But in SCA we do not talk about how and where the service is exposed 
(except when an explicit URI is provided). If it is a local interface 
then it may not be exposed at all. A service may be available only with
the bindings specified in SCDL, it may be made available with additional
bindings. It may be made available with the same bindings on two 
different network endpoints -- perhaps one for clients inside the 
firewall and another (portmapped) endpoint available outside the 
firewall (perhaps with limited capabilities).

When binding.ws is used, it can specify a network endpoint (through the
URI attribute or by pointing to a WSDL service/port) or multiple 
endpoints (by pointing to a WSDL service). OR it may not specify the 
endpoint at all (by pointing to a WSDL binding) or using defaults.

If the URL is explicitly provided in the SCDL then of course it is known
apriori. If not, it is indeed left to the deployer/runtime to do the 
magic, where at runtime the reference knows where the SCA service is 
located. In fact, I believe it is perfectly ok for the runtime to not 
even generate a WSDL service/port element, if the binding.ws pointed to
a WSDL binding element. All the WSDL service/port is going to do is 
provide the URL and the runtime/deployer may know exactly what value to
inject automagically and transparently.

All this is to say that we should not impose additional restrictions on
the generated WSDL service element than those that are required. The 
restrictions that are required are:
1) restrictions imposed by intents.
2) There must be at least one service/port in the generated wsdl that 
matches the SCDL interface and the SCDL binding.

Some of the examples of restrictions that do *not* make sense to me are:
1) how many wsdl documents should be there. Eg the binding and service
elements can be in the same wsdl or different wsdl (with appropriate 
include/import).
2) how many ports a service should contain.
3) whether the generated WSDL contains just one service element or many

Comments?

-Anish
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