W3C home > Mailing lists > Public > public-owl-wg@w3.org > September 2008

Re: Issue-130 (conformance)

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 03 Sep 2008 21:08:10 -0400
To: Jim Hendler <hendler@cs.rpi.edu>
cc: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>, W3C OWL Working Group <public-owl-wg@w3.org>
Message-ID: <23532.1220490490@ubuhebe>

> FWIW, I would not be happy with MUST, could abstain from SHOULD, much  
> prefer MAY.  Despite what Bijan wrote, I think Ivan made a valid  
> point.  I also think, as a general "marketing" point that any time we  
> use MUST we risk losing implementations that would otherwise be  
> getting more people to use OWL.
>   Please note that this is an opinion, not a fact, as there is no  
> correct answer to which of these words to use, organizations need to  
> use their best judgment, and my best judgment is reflected above.

I'm afraid the options weren't clear enough.  The rephrasing today does
not increase anyone's implementation burden, except in that it helps
motivate doing theorem-1 checking.

What I'm trying to avoid is conformant entailment checkers saying
"False" (saying the given OWL entailment does not hold) when the
entailment actually *does* hold.  The RL Conformance text until today
allowed that in some cases.

      -- Sandro

>   -Jim H.
> AC Rep, RPI
> On Sep 3, 2008, at 4:35 PM, Ian Horrocks wrote:
> >
> > The idea we came up with on the teleconf was to say that  
> > implementations MUST issue a warning when they can't be sure about a  
> > False answer, and to add that implementations not wanting to check  
> > the conditions could simply return Unknown instead of False. On  
> > closer examination, this doesn't make total sense and/or seems  
> > unnecessarily complicated.
> >
> > In the first place, it is strange to say that implementations MUST  
> > do something, and then say that they can do something else instead.  
> > In the second place, it doesn't seem to make much sense to return  
> > False with a warning that this answer can't be trusted -- surely it  
> > would be much more sensible to return Unknown under these  
> > circumstances. This would allow the conformance conditions on OWL RL  
> > checkers to be greatly simplified, i.e., to say that they can only  
> > return False when the entailment doesn't hold (just like for the  
> > other checkers). We could then add a note for implementers pointing  
> > out that Theorem 1 tells them just when it is safe for rule-based  
> > implementations to return False (when the conditions are satisfied  
> > and the entailment isn't found by the rules). The note can also say  
> > that if they don't want to implement the check they can simply avoid  
> > returning False.
> >
> > To make this clearer/more concrete, I implemented this in the  
> > Conformance document [1].
> >
> > Still to do: add something about what this would mean in the case of  
> > query answering, to the effect that a warning MAY/SHOULD/MUST be  
> > issued if "Unknown" would be the answer to any relevant entailment  
> > problem.
> >
> > No doubt you will let me know what you think.
> >
> > Ian
> >
> > [1] http://www.w3.org/2007/OWL/wiki/Conformance
> >
> "If we knew what we were doing, it wouldn't be called research, would  
> it?." - Albert Einstein
> Prof James Hendler				http://www.cs.rpi.edu/~hendler
> Tetherless World Constellation Chair
> Computer Science Dept
> Rensselaer Polytechnic Institute, Troy NY 12180
Received on Thursday, 4 September 2008 01:09:57 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:42:06 UTC