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Subject: Re: [sca-bindings] Comments on proposed resolution to BINDINGS-126
I can address the questions of relationship to the SCA Policy FW spec. In
short, the reason is because the SCA Policy FW spec is a framework spec,
not a policy spec. It's main job is to provide a policy language neutral
(WS-Policy is not the only game in town) framework for applying policy to
SCA compositions, in the same way that the assembly spec is component
implementation neutral. Since bindings are one of the main targets for
policy, it seems natural that a particular binding type would align itself
with a specific policy language. In fact, the Policy FW spec recognizes
this by providing a means for a policySet to indicate what kind of binding
it can be applied to. We do not have the reverse notion in the FW such
that a binding type could indicate what policy languages it can support,
except via documentation from the implementor of that binding type.
Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:booz@us.ibm.com
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|Eric Johnson <eric@tibco.com> |
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|Simon Holdsworth <simon_holdsworth@uk.ibm.com> |
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|sca-bindings@lists.oasis-open.org |
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|04/09/2010 12:42 PM |
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|Re: [sca-bindings] Comments on proposed resolution to BINDINGS-126 |
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I think we should kick this over to the policy TC.
Assembly says that you must support policy and binding.ws, and it doesn't
make sense to me that the binding.ws spec should be dictating that
WS-Policy is supported, since anyone reading the SCA-Policy spec would
expect to find that mandate in that spec. If the Policy TC hasn't mandated
this up until now, it doesn't make sense to me that the bindings TC should
jump in - and I'd sure like to know why the Policy TC hasn't mandated it,
if that question has come up.
Feels to me like the policy TC should be dealing with some of the issues we
identified on the call, and that Simon notes below:
If we don't require support for any specific WS-Policy assertion, how
do we test?
How do we reconcile WS-Policy statements that we do find, and
potential conflict with stated intents?
(and one I've just thought of) Are the requirements different
depending on whether the binding is on a service or a reference?
The problem seems different depending on whether you're defining a binding
on a service or a reference.
On a reference, a human has to verify that the relevant intents match
the details of the specific binding.
On a service, mostly these details will be discarded, won't they? If
not, what does it mean to have policy information in three places -
intents, policySets, and in the WSDL? Who wins? Is it even a
contest?
Although I've not thought about it too hard, I can't see that anything
except the intervention of a human can resolve the potential discrepancies
between policy intents and actual WS-Policy statements found in a WSDL. At
that point, some poor administrator/deployer has to look at the WSDL
component pointed at by wsdlElement, look at the policy intents, and look
at any policySets that have been applied to satisfy that intent, and then
that admin will typically(?) discard the WS-Policy information in the WSDL
component.
So then what's the point of having WS-Policy statements in the referenced
WSDL? I'd actually go the other direction, if we were to state anything
normative, and suggest that an SCA Runtime MAY discard any WS-Policy
statements found in the WSDL pointed at by wsdlElement. That would make
more sense to the deployer.
All of the above circles around a question for me - do we collectively have
enough understanding of implementation considerations to know what should
be normatively asserted?
I should add, I'm not trying to play the role of wet blanket. I suspect
most, or even all implementations, if/when they support any sort of policy
on the wsdlElement target, or expose policy in generated WSDL, will use
WS-Policy, because there aren't really any alternatives. I just don't know
the details of how they'll support it. Normative requirements here remind
me of a tar pit.
-Eric.
On 04/09/2010 03:00 AM, Simon Holdsworth wrote:
Mike,
Here's my comments on the proposal that's in JIRA:
> A binding.ws implementation MUST support the WS-Policy
specification and MUST:
"MUST support the WS-Policy specification" seems a bit vague to me -
isn't that what the following list defines in more detail?
Also, I don't think we've used "binding.ws implementation" anywhere
in normative statements, to be consistent this would be "SCA runtime"
> a) accept WS-Policy statement in any supplied WSDLs
Basically I believe what we are saying here is that an SCA runtime
MUST not reject a WSDL simply because it includes WS-Policy
statements, which is perhaps somewhat different to "accept"ing
WS-Policy statements.
> b) advertise any policies applied to a service using the WS-Policy
language
Would the default WSDL generation rules be impacted by this? Are we
saying that all policies that are applied to be a service MUST be
represented as WS-Policy statements in the WSDL, or are we saying
that IF there are any policy statements in the WSDL, they must at
least be expressed using WS-Policy? I'm not sure how we could check
that any WSDL extensibility elements present in other namespaces are
policy-related rather than anything else.
> c) accept WS-Policy statements in SCA policySets
As above
> d) use the WS-Policy policy intersection rules when matching
policies between a reference and a service
[BWS20038]
I think more discussion is needed around what happens with the
combination of WS-Policy statements in the WSDL referred to by a
binding.ws and the SCA policy sets. From the Web Service binding
spec:
"If the binding is for an SCA reference, the set of available ports
for the reference consists of the ports in the WSDL service that have
portTypes which are compatible supersets of the SCA reference as
defined in the SCA Assembly Model specification [SCA-Assembly] and
satisfy all the policy constraints of the binding."
Does this issue affect the definition of the "set of available
ports"? Would they need to satisfy all the policy constraints of the
binding as well as all the policy constraints described in the WSDL?
Regards, Simon
Simon Holdsworth
STSM, SCA Bindings Architect; Master Inventor; OASIS SCA Bindings TC
Chair, AT&T and Boeing Lab Advocate
MP 211, IBM UK Labs, Hursley Park, Winchester SO21 2JN, UK
Tel +44-1962-815059 (Internal 245059) Fax +44-1962-816898
Internet - Simon_Holdsworth@uk.ibm.com
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with
number 741598.
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