Re: [poe] isNeccessaryFor

@riannella and @simonstey I stick to my question: is isNecessaryFor 
what we need or do we want to communicate: a constraint related to an 
Action must be checked at the time of exercising the Action.

Re Renato's thoughts above:

Re "What does C1 odrl:and C2 mean": right, both MUST be satified. And 
right: how to deal with "no result of C1 is available" is not 
discussed anywhere in the ODRL specs.

Re "C1 odrl:isNeccessaryFor C2": first: why "both MUST be satisfied", 
this is currently nowhere defined. Re "as soon ...": exactly that is 
going in the wrong direction - if the Left Operand of C1 is Count then
 this constraint should not be processed on 1 February, 1200 GMT and 
this result is used for the next 3 weeks as the count of uses will 
increase in this period - and that's the issue. The same applies to 
dynamic time values - e.g. delivered by a rightOperandReference: this 
should be checked at the time of executing the Action not 3 hours 
before that.

Re both issues above: ODRL needs a generic rule about how to deal with
 "while processing a Constraint expression a result cannot be 
generated" - this is also important for odrl:and and not only for 
isNecessaryFor. (Btw: in an odrl:and Constraint Relation C1 is not 
unnecessary for C2.) I'm aware of Simon's concern at one of the recent
 calls: how to define exactly "a result cannot be generated": reasons 
could be a resource referenced by rightOperandReference delivers an 
explicit error status (that's the easy variant) or the resource does 
not deliver any response for 15 minutes now (not so easy: should ODRL 
or something else define a time limit ??). And what about syntax 
errors: e.g. the duty to pay has a rightOperand value of "abXZ" ?

Re "circular chaining": you are right, a single Constraint Relation 
can combine only 2 atomic Constraints. Double check: CR1 combines C1 
and C2, CR2 combines C2 and C3, CR3 combines C3 and C1: could this be 
considered as "circular chaining" - ? @simonstey 

Re your re Item 8: no, getting a result of a constraint is not the 
same as the constraint is satified. As said above how to deal with 
missing results is an open issue.


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Received on Wednesday, 1 February 2017 14:26:25 UTC