Re: Constraint V Refinement

@victor

>  I do not see a great difference between refinement or constraint because
its interpretation is not defined (cf. examples in a testbed where an
algorithm must behave differently in each case),

well the idea was to make a distinction between (see discussion here
https://github.com/w3c/poe/issues/282):

   1. constraints that describe the world state under which a rule becomes
   effective (Rule --odrl:constraint--> Constraint),
   2. constraints that refine party/asset/action of a rule such that the
   refined party/asset/action represents those affected by the Rule
   (Action/AC/PC --odrl:refinement--> Constraint)

[image: image.png]

here are a few links to our discussions back in the day:

   - https://github.com/w3c/poe/issues/211#issuecomment-325198929
   - https://github.com/w3c/poe/issues/191#issuecomment-315283129
   - https://github.com/w3c/poe/issues/112
   - https://github.com/w3c/poe/issues/226 (discussion about refinements at
   the end)

> therefore the difference is only philosophical to me

well, we explicitly prohibit outcomes of refinements to result in the empty
set, see e.g.

   - https://w3c.github.io/poe/model/#constraint-action
      - Note: The outcome of applying refinements to an Action SHOULD NOT
      result in a null operation.
   - https://w3c.github.io/poe/model/#constraint-asset
   - Note: The outcome of applying refinements to an AssetCollection SHOULD
      NOT result in a null set.

while this comes with its own slew of issues, restrictions that for example
can't be satisfied at all can technically not be used as refinements

> Can someone suggest improved definitions/clarifications for these:
>  - A Rule MAY include the constraint property to indicate a condition on
the Rule.
>  - An Action MAY include the refinement property to indicate a Constraint
that narrows the semantics of the Action operation directly.

but not for:
- An AssetCollection MAY include a refinement property to indicate the
refinement context under which to identify individual Asset(s) of the
complete collection.
- A PartyCollection MAY include a refinement property to indicate the
refinement context under which to identify individual Party(ies) of the
complete collection.
?

Btw in the BP document, deliveryChannel is used as refinement on the action
https://w3c.github.io/odrl/bp/#x2-1-narrowing-the-applicability-of-an-action

cheers, simon

On Fri, 8 Apr 2022 at 07:33, Renato Iannella <r@iannel.la> wrote:

> I think we need to provide guidance on the difference.
>
> Otherwise, different implementations may use deliveryChannel as an action
> refinement  in one Policy, then as a rule constraint in another.
> (this would be good content for the Best Practices guide:
> https://w3c.github.io/odrl/bp/)
>
> Can someone suggest improved definitions/clarifications for these:
>   - A Rule MAY include the constraint property to indicate a condition on
> the Rule.
>   - An Action MAY include the refinement property to indicate a Constraint
> that narrows the semantics of the Action operation directly.
>
> Cheers - Renato
>
>
> On 8 Apr 2022, at 00:20, Víctor Rodríguez Doncel <vrodriguez@fi.upm.es>
> wrote:
>
> Hi,
>
> I do not see a great difference between refinement or constraint because
> its interpretation is not defined (cf. examples in a testbed where an
> algorithm must behave differently in each case), therefore the difference
> is only philosophical to me. And even in this case unclear: I would have
> said constraint, though, for the deliveryChannel, and if refinement,
> refinement of the action (this would be like an "adverb" modifying the
> action rather than an "adjective" qualifying the asset)
>
> Regards,
> Víctor
>
> > Is the deliveryChannel a refinement on ‘stream’ or a constraint on the
> rule?
>
> refinement on the asset i.e. the video itself? e.g., => "you can stream
> (action) videos whose deliveryChannel is YouTube (asset with
> deliveryChannel == YT)
>
> br, simon
>
>
> On Thu, 7 Apr 2022 at 02:42, Renato Iannella <r@iannel.la> wrote:
>
>>
>> Hi all, we generally define the constraint property as a “condition on
>> the rule” and the refinement property as “narrow the semantics of the
>> action”.
>>
>> So, for example temporal and geospatial conditions apply to the rule, and
>> printing at most 5 times is a refinement to print.
>>
>> My question is how to interpret this difference with other use cases,
>> such as:
>>  - you can stream (action) a video (asset)  on YouTube (deliveryChannel)
>> only?
>>
>> Is the deliveryChannel a refinement on ‘stream’ or a constraint on the
>> rule?
>>
>> Thanks…Renato
>>
>
>
> --
> Víctor Rodríguez-Doncel
> D3205 - Ontology Engineering Group (OEG)
> Departamento de Inteligencia Artificial
> ETS de Ingenieros Informáticos
> Universidad Politécnica de Madrid
>
> Campus de Montegancedo s/n
> Boadilla del Monte-28660 Madrid, Spain
> Tel. (+34) 910672914
> Skype: vroddon3http://cosasbuenas.es
>
>
>
>