[ISSUE-61] How are mayProvide intents on bindings satisfied - PROPOSAL

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

Folks,

Here is a proposal which resolves POLICY-56.
 First a preamble to give some reasoning for what follows:
 
Where a Binding type declares @mayProvide="a list
of intents", what this means is: 

- an instance of this Binding type can provide any of the intents in the
list 

- each intent in the list is provided by the binding instance WHEN the
list of intents applied to the binding instance includes that intent
(I assume that IF the @mayProvides list of intents includes an unqualified
form of a qualifiable intent, then any qualified form of the intent applied
to 
the binding instance means that the qualified form of the intent is what
is actually provided) 

- "applied to the binding instance" means that the intent is
declared EITHER directly on the binding instance OR on one of its parent
elements 


The resolution of POLICY-56 is worth reading in this light:

- a binding type MAY have parameters (other than intents & policy sets)
that affect policy related attributes of the binding 
BUT IF this is the case and a particular binding instance has those parameters
set in a way which is in conflict with the intents
and/or policySets applied to a binding instance, THEN the runtime must
raise an error.

OK, here are my proposed changes to the Policy Spec (WD-08):

Replace lines 1243 - 1247 with: 

The set of provided intents for a binding instance is the union
of the set of intents listed in the 
“alwaysProvides” attribute and the set of intents listed in the “mayProvides”
attribute of of its binding type. 
The capabilities represented by the "alwaysProvides" intent set
are always present, irrespective of the 
configuration of the binding instance. Each capability represented by the
"mayProvides" intent set is 
only present when the list of intents applied to the binding instance (either
applied directly, or inherited) 
contains the particular intent (or a qualified version of that intent,
if the intent set contains an unqualified 
form of a qualifiable intent). When an intent is directly provided by the
binding type, there is no need to 
apply a policy set that provides that intent. 


Replace lines 1378 - 1380 with:

For a binding instance, the set of intents listed in the @alwaysProvides attribute of the binding type definition
plus the set of intents listed in the binding type’s @mayProvides attribute



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

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