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Subject: RE: [sca-policy] ISSUE POLICY-18 : Should qualifiable intents have adefault qualifier
- From: Mike Edwards <mike_edwards@uk.ibm.com>
- To: "OASIS Policy" <sca-policy@lists.oasis-open.org>
- Date: Tue, 27 Nov 2007 09:27:23 +0000
Michael,
"
In my opinion, my original words were easier to understand. Does
that description miss something?"
YES, it misses the cases where there
are two or more qualified intents "competing" with each other
to select out policy sets. Two
different intents potentially make different selections. How to resolve
such a conflict? Even my words
leave it vague as to which one "wins" - it just says that choosing
in
favour of one can't mess up the resolution
of the other one.
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
"Michael Rowley"
<mrowley@bea.com>
27/11/2007 07:44
|
To
| Mike Edwards/UK/IBM@IBMGB, "OASIS
Policy" <sca-policy@lists.oasis-open.org>
|
cc
|
|
Subject
| RE: [sca-policy] ISSUE POLICY-18 : Should
qualifiable intents have a default qualifier |
|
From: Mike Edwards [mailto:mike_edwards@uk.ibm.com]
Sent: Thursday, November 22, 2007 9:00 AM
To: OASIS Policy
Subject: RE: [sca-policy] ISSUE POLICY-18 : Should qualifiable intents
have a default qualifier
Michael,
I think there is a need to think through the meaning before worrying about
the words.
There is a problem in getting a clean selection of policyset(s) in the
case where there are two or more
qualified intents in the mix being used to select out the policysets.
The use cases 1) and 2) below are clear. The default qualifier in
the intent definition acts as a tie breaker
for otherwise ambiguous cases. So an intent intentA is treated
as if it were written "intentA.defaultQ" for
usecases 1) and 2) and is interpreted accordingly.
Case 3) is less clear to me.
Here let's assume that @requires="intentA" is specified for some
element.
This will pick out policySets which have @provides="intentA"
and in this case, the default qualifier in the intent
definition is not used at all (right?).
Right.
If the policySet(s) have their own internal
default, that gets used.
However, for policySets which @provides="intentA.someQ", the
idea is that the default qualifier in the intent
definition is used to select out ONLY those policySets which have @provides="intentA.defaultQ"
(right?)
It is as if @requires="intentA" is interpreted as if @requires="intentA.defaultQ".
Only in cases where it is used
to disambiguate between two different policySets, one that provides “intentA.defaultQ”
and the other that provides “intentA.someOtherQ”. It is only used
as a tie breaker. Here was my proposed rule: “If
there are multiple matching policy sets whose @provides lists are identical
except that each provides a different qualifier for the same qualifiable
intent, then only the policy set that provides the qualifier that was defined
as the default qualifier will be used.
“
This leads to entertainment if there are multiple qualified intents: @requires="intentA
intentB"
This is now interpreted as if @requires="intentA.defaultQ intentB.defaultQB".
The result of this is potentially
to fail to select any policySet at all.
Not quite, as noted above.
A policySet with @provides="intentA intentB" will be selected
OK.
But a policySet with (say) @provides="intentA.someQ intentB"
will now fail selection as it does not provide
intentA.defaultQ. If this is the only policySet providing intentB,
the whole process will fail, if I understand the
proposal below. If it is supposed to work, then the wording below
simply doesn't say enough about the
selection process.
What was the intention here?
No, that isn’t how it works.
The default was only supposed to be used as a tie-breaker, when more
than one policySet would qualify.
If the default qualifier is really a "tie breaker", then it should
not be used until the point where the (original)
process has (potentially multiple) sets of policySets that satisfy all
the stated intents. These can be
potentially winnowed using the default qualifiers, but there may be conflict
between the default qualifiers
for different intents and there must be some conflict resolution process.
"Remove from the set of policySets each of those policySets which
provide qualified intents for the
unqualified intents in the set of intents where the provided qualified
intent does not match the default qualifier for
the intent, IF the removal of that policySet does NOT cause some (other)
intent in the set of intents to become
unsatisfied by the remaining group of policySets"
UGH !
Indeed it is tricky to get
the right words. In my opinion, my original words were easier to
understand. Does that description miss something?
Reminder (so you don’t have
to scroll up): “If there are multiple
matching policy sets whose @provides lists are identical except that each
provides a different qualifier for the same qualifiable intent, then only
the policy set that provides the qualifier that was defined as the default
qualifier will be used. “
Michael
Or is my brain just too small to handle this stuff.
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
"Michael Rowley"
<mrowley@bea.com>
20/11/2007 21:48
|
To
| <sca-policy@lists.oasis-open.org>
|
cc
|
|
Subject
| RE: [sca-policy] ISSUE POLICY-18 : Should
qualifiable intents have a default qualifier |
|
We discussed a potential solution to this issue on yesterday's policy TC.
Here is a proposal that I believe fits with the discussion that we
had (and fulfills the action item I took on the call).
First, it is worth noting the situations where the current approach of
having a default qualifier in an intent map, doesn't work:
1) Policy sets aren't used because binding.sca is being used, and that
binding uses intents directly, rather than using policy sets.
2) If a binding specifies a qualifiable intent in its list of @mayProvide
intents, then no policy sets or intent maps will be used.
3) When policy sets for qualified intents are specified separately, rather
than being part of a single intent map, then there is no place to put a
default qualifier. This approach is valuable for qualifiable intents
that may gain additional qualifiers over time.
To handle these situations, a intent definition will get a new attribute
called @defaultQualifier. The value of the attribute is the name
of a qualifier (so the full quaified intent would be "<qualifiable
intent name>.<qualifier name>").
This default has lower priority than defaults that might be found in intent
maps. So, if some construct which includes intent "a" in
its @requires list matches against a policySet that includes "a"
in its @provides list, then that policy set will be used, irrespective
of any default qualifier listed in the intent definition for "a".
If "a" is qualifiable, then the policy set that provides
it will most likely include an intent map, although that isn’t strictly
necessary.
The policy set matching algorithm in section 4.10 will need to be modified.
Step E currently reads:
E. Choose the smallest collection of additional policySets that match all
remaining required intents.
This will need the following addition:
If there are multiple matching policy sets whose @provides lists are identical
except that each provides a different qualifier for the same qualifiable
intent, then only the policy set that provides the qualifier that was defined
as the default qualifier will be used.
I know that the above text is quite complicated, so I hope someone will
suggest how it can be made simpler.
I think we also need to address intents offered by the @mayProvide list
for bindings. I think the rule should be something like the following:
If a binding lists a qualifiable intent in its @mayProvide list, then the
binding is assumed to support any of the qualifiers for that intent (i.e.
the binding will do the right thing if the qualified intent is required).
If only the qualifiable form of the intent is required, then the
behavior is the same as if the qualified intent that corresponds to the
default qualifier had been required.
Michael
-----Original Message-----
From: Joshi, Kaanu [mailto:Kaanu.Joshi@patni.com]
Sent: Friday, October 19, 2007 1:06 PM
To: OASIS Policy
Subject: [sca-policy] ISSUE POLICY-18 : Should qualifiable intents have
a default qualifier
Hi folks,
The link for this issue in the SCA Policy TC JIRA: http://www.osoa.org/jira/browse/POLICY-18
Regards,
Kaanu Joshi
________________________________________
From: ashok malhotra [ashok.malhotra@oracle.com]
Sent: Thursday, October 18, 2007 9:29 PM
To: OASIS Policy
Subject: [sca-policy] NEW ISSUE: Should qualifiable intens have a default
qualifier
TARGET: SCA Policy Framework
DESCRIPTION : The transaction proposal needs to capture default
qualified intent behavior
outside of a policySet.
PROPOSAL:
PROVENANCE: SCA-182 by booz on 2006-10-23 08:49:45
--
All the best, Ashok
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