Fwd: Re: Fwd: On complex constraints

Dear all,

Please see below response from Piero regarding representing complex
constraints in DL.

Best Regards,
Sabrina


-------- Forwarded Message --------
Subject: Re: Fwd: On complex constraints
Date: Thu, 3 Nov 2016 11:26:05 +0100
From: Piero Bonatti <pieroandrea.bonatti@unina.it>
To: Sabrina Kirrane <sabrina.kirrane@wu.ac.at>, Axel Polleres
<axel.polleres@wu.ac.at>
CC: Simon Steyskal <simon.steyskal@wu.ac.at>

Hi everybody,

In DL one can use concrete domains, in principle. It would look more or
less like this:

declare that Photos have:
 a property "about" whose range includes football games;
 a concrete feature "hasPublicationDate" with datatype Date.

In turn football games have a concrete feature "hasEndTime".

then assert something like:
Subclass( PublishablePhoto
          (>= hasPublicationDate about.hasEndTime+1))

(note: operator '+' might not be directly supported in that context, but
one can overcome this limitation using an auxiliary feature to hold the
result of the sum)

OWL 2 does not (yet) support linear constraints like the above. However:

1) There are proposals to support them, see
https://www.w3.org/TR/2012/NOTE-owl2-dr-linear-20121211/

2) The theory is all there (syntax, semantics, decidability), see
http://sunsite.informatik.rwth-aachen.de/Publications/CEUR-WS//Vol-86/13-Lutz.ps

3) The RacerPro engine already supports linear constraints, see
http://www.dblab.ntua.gr/~gtsat/collection/RDF%20stores/Racer_whitepaper.pdf

there might also be more engines supporting linear constraints, but I
have no time to look for them right now

cheers
Piero

PS: the syntax I used above is not exactly the syntax used in 1), nor
the syntax used on 3), so if you need to show something formally correct
then you'll have to adapt my encoding accordingly.

On 11/10/2016 00:04, Sabrina Kirrane wrote:
> Hi Axel & Piero,
>
> On this weeks W3C POE call we were discussing how we can add complex
> constraints (i.e. constraints on constraints) to ODRL.
>
> At the moment it is possible to associate 0:M duties with a permission.
> Duties can have 0:M constraints, and each one must be satisfied in order
> to gain access to the resource (N.B OR and XOR operators are currently
> not supported, however there is talk about reintroducing them).
>
> Going beyond simple boolean operators TR have indicated that there is a
> need to express relations between constraints.
>
> For example they need to be able to express relative events e.g. a
> relative constraint could state a photo may be published "1 hour after
> the football game ended".
>
> How would you express this in RDF? OWL?
>
> Bet regards,
> Sabrina
>
>
> -------- Forwarded Message --------
> Subject: 	On complex constraints
> Resent-Date: 	Fri, 23 Sep 2016 09:37:59 +0000
> Resent-From: 	public-poe-wg@w3.org
> Date: 	Fri, 23 Sep 2016 11:43:20 +0200
> From: 	Víctor Rodríguez Doncel <vrodriguez@fi.upm.es>
> To: 	public-poe-wg@w3.org
>
>
>
> Dear all,
>
> I did not verbally express my view as I did not feel capable to. I'll
> try to write it:
>
> Simple constraints are in ODRL logical expressions, whose truth value
> might be evaluated. With ODRL we can express for example:
>
> R1: industry = academy
> R2: count <=5
>
> We have in ODRL the ability to define logical expressions with two
> variables: an "operator", a "rightOperand" and a left operand (called
> "name").
> We can even combine these expressions with connectives (extended model):
> AND, OR, NOT.
> However, we are moving within the limits of logic and we cannot evaluate
> algebraic expressions.
> Namely, we would like to have:
>
> R3: publicationTime > (asset.FootballMatchEndTime + 1 hour)
>
> We cannot define algebraic formulas, nor variables. We would like to
> have something like:
>
> var1: asset.FootbalMatchEndTime + 1 hour
> R4: publicationTime > var1
>
> So even if we use reification, we can't still represent the addition
> operation.
> I think adding these features would dramatically increase the complexity
> of the model...
>
> Víctor
>
> El 23/09/2016 a las 9:49, Renato Iannella escribió:
>> Raw minutes from
>> yesterday: https://www.w3.org/2016/09/22-poe-minutes.html
>>
>> Renato Iannella, Monegraph
>> Co-Chair, W3C Permissions & Obligations Expression (POE) Working Group
>>
>
>

Received on Monday, 7 November 2016 12:33:45 UTC