Re: Publications about OWL (1 or 2) Full

ON the Eagle Example:

> :Species a owl:Class .
> :Eagle a :Species, a owl:Class ;
> rdfs:subClassOf :Animal .
> :billy a :Eagle .
>
> This is valid OWL 2 DL.
>
> Then, with a SPARQL 1.1 query with OWL 2 DL entailment regime, I can get
> the pairs <species,individualmemberofthespecies>:
>
> SELECT ?species, ?member WHERE {
> ?species a :Species .
> ?member a ?species .
> }
>

> Yes, this is allowed.

So if this returns ?species as Eagle and ?member as Billy, then SPARQL must
not know it is only a pun. It thinks the two are the same.  Maybe it is just
a syntactic link with little or no semantic import.Intriguing. I'll have to
try this out.

This is a bit better than I thought. Thanks for the clarification.


On Thu, May 19, 2011 at 12:01 PM, Markus Krötzsch <
markus.kroetzsch@comlab.ox.ac.uk> wrote:

> On 19/05/11 18:58, Antoine Zimmermann wrote:
>
>> First, thanks to you Michael and Markus for your replies.
>>
>> Now, Michael,
>>
>>  <snip>
>
>
>>>>>
>>>> Fortunately, OWL 2 now allows a useful form of simple meta-modelling
>>>> now,
>>>> so that you can indeed have meta classes and use classes as subjects and
>>>> objects of properties.
>>>>
>>>
>>> The logical inferences that OWL 2 DL tools draw from this are limited,
>>> but
>>>
>>>> may still be more than what any particular OWL 2 Full reasoner would
>>>> give
>>>> you (depends on the OWL 2 Full reasoner you have -- I am not aware of
>>>> much
>>>> implementation work there beyond OWL 2 RL).
>>>>
>>>>
>>> Hmm, I know there is some limited punning, but these are two different
>>> things, not one thing appearing in two different places. The inference is
>>> very limited.
>>>
>>
>> What Markus says here I guess is that, in spite of the limitations of
>> the punning mechanism, a full-fledged OWL 2 DL reasoners will likely
>> infer more things than *currently existing* incomplete OWL Full reasoners.
>>
>
> Right. We know that there cannot be a tool that computes all consequences
> of OWL with "proper" meta modelling, and we also know that some forms of
> meta modelling can even lead to intricate inconsistencies that make the
> whole ontology language paradoxical (PF Patel-Schneider's paper "Building
> the Semantic Web Tower from RDF Straw" alludes to this issue). So it seems
> that a tool that obtains all consequences of plain OWL constructs, and that
> can still handle some meta modelling is not such a bad choice, even if it is
> called "OWL DL reasoner" ;-)
>
>
>
>>
>>> I don't think there is a way to nicely handle the species example where
>>> Species is a class with instance Eagle with instances being individual
>>> eagles.
>>>
>>
>> No problem:
>>
>> :Species a owl:Class .
>> :Eagle a :Species, a owl:Class ;
>> rdfs:subClassOf :Animal .
>> :billy a :Eagle .
>>
>> This is valid OWL 2 DL.
>>
>> Then, with a SPARQL 1.1 query with OWL 2 DL entailment regime, I can get
>> the pairs <species,individualmemberofthespecies>:
>>
>> SELECT ?species, ?member WHERE {
>> ?species a :Species .
>> ?member a ?species .
>> }
>>
>
> Yes, this is allowed.
>
>
>
>>
>>> I also do not think there is a robust solution to the classes as values
>>> problem.
>>>
>>
>> What do you mean by "classes as values problem"?
>>
>>
>>  An insightful discussion of meta modelling semantics -- the one of
>>>> OWL 2 DL
>>>> (punning) and a stronger one -- is found in the paper:
>>>>
>>>> Boris Motik. On the Properties of Metamodeling in OWL. Journal of
>>>> Logic and
>>>> Computation, 17(4):617–637, 2007.
>>>>
>>>>
>>>>  Thanks, I just had a look. It is intersting, and geared more for the
>>> theorist than the practitioner. Do you know of a more practice-focused
>>> paper that gives examples of what you can and cannot do with OWL2
>>> metamodelling, compared to OWL-Full?
>>>
>>
> Indeed, this paper is more on the logical side of the discussion, though I
> still found it quite accessible. Especially, it has some examples of
> consequences that one looses under the weak meta modelling of OWL 2.
>
> I am not aware of a treatment of this issue that is using OWL or RDF
> terminology. This may not make it easier to understand, since the issues of
> metamodelling are often complicated by nature -- the straw tower paper
> mentioned above uses the RDF data model but still requires some thought to
> understand the key issues raised there.
>
>
>
>>>
>>>  A big advantage of OWL 2 DL in this respect is that it makes it legal to
>>>> state such meta-knowledge without violating any constraints of the
>>>> language.
>>>> The OWL Full semantics may still formally lead to more consequences,
>>>> but in
>>>> practice what matters is how many of the total consequence any tool will
>>>> actually give. So the DL approach could be a good compromise
>>>> (especially to
>>>> "make meaning clear" beyond purely logical/formal aspects).
>>>>
>>>>
>>> I'm not sure what you mean by "make meaning clear" as a good DL
>>> compromise.
>>> The example from that paper is the need to represent Eagle as an instance
>>> of Species so you can e.g. say it is on the engangered list. DL forces
>>> you
>>> to represent Eagle as an as an individual that can not ever have any
>>> instances. But this is patently untrue -- to that extent, it obfusticates
>>> meaning. If OWL2 metamodellign lets me do this, I'll be surprised and
>>> delighted.
>>>
>>
>> Punning means that you can use the URI of an individual in place of the
>> URI of a class. Therefore, :Eagle, as a class, can have instances (like
>> :billy above) and as an individual it can belong to a class (like
>> :Species). However, :Eagle-the-individual is different from
>> :Eagle-the-class, although they share the same identifier.
>>
>
> Exactly. This is of course a cheap form of meta modelling, but it seems
> that it goes a surprisingly long way in practice. Many use cases are really
> about modelling several "layers" of the domain of interest, but have only
> little interaction between these layers. Here is an example where one would
> see the limitation:
>
> Assume you have Eagle and Hawk as classes, and you have an individual
> Tweety who is said to have the species Eagle, and to have the species Hawk
> (as individuals). Assume further that there is a cardinality restriction
> that requires "has species" to be functional. Then implicitly we derive that
> Eagle and Hawk are the same individuals. With punning, nothing else happens.
> With "true" meta modelling, the classes Eagle and Hawk would also be
> inferred to be the same, with all the consequences that this could have.
>
> I am not sure if this is a practically relevant limitation.
>
> Cheers,
>
> Markus
>
>
>
>
>>>> I think the more important case where ontologies go beyond OWL DL is
>>>> due to
>>>> the structural constraints related to transitivity and property
>>>> chains (e.g.
>>>> it is easy to get forbidden cycles in property chain dependencies).
>>>> But the
>>>> interesting difference to the earlier meta-modelling limitations of
>>>> OWL 1 DL
>>>> is that in these cases, the semantics of OWL DL is in principle still
>>>> meaningful and well-defined in its common first-order logic
>>>> framework. It is
>>>> simply known that computing consequences of this semantics becomes
>>>> undecidable, and thus the decidability-loving DL tools reject the inputs
>>>> right away.
>>>>
>>>> But again anybody who would venture to implement OWL Full reasoning
>>>> could
>>>> also look into "OWL DL reasoning for ontologies violating the structural
>>>> restrictions." This task might be easier to solve in practice since one
>>>> could probably reuse existing algorithms and tools to solve part of the
>>>> problem. It is also part of ongoing research to weaken the structural
>>>> restrictions further, so one already knows of complete algorithms
>>>> that could
>>>> achieve this in some cases that OWL DL excludes.
>>>>
>>>> Also note that "FULL" and "DL" now refer to syntactic languages only.
>>>> The
>>>> semantic distinction is now made between "direct semantics" and
>>>> "RDF-based
>>>> semantics". This helps a bit to avoid confusion between syntax and
>>>> semantics. So my last remark was about finding ways to evaluate (more
>>>> of)
>>>> OWL 2 FULL under direct semantics.
>>>>
>>>> Cheers,
>>>>
>>>> Markus
>>>>
>>>>
>>>>  I have no hard evidence, but I feel certain that there are plenty of
>>>>> cases when the penalties of OWL Full are on balance small enough
>>>>> compared to the gains of expressive convenience and clarity of OWL
>>>>> Full.
>>>>>
>>>>> I would love to see someone look into this. I would love it if someone
>>>>> tried to create a reasoner that handled OWL Full as efficiently as
>>>>> possible.
>>>>>
>>>>> Notice how many responses you got to this message in the past few
>>>>> weeks?
>>>>> That may reflect how much people in the community care about OWL Full!
>>>>>
>>>>> Michael
>>>>>
>>>>> Michael
>>>>>
>>>>> On Sat, Apr 23, 2011 at 1:05 AM, Antoine Zimmermann
>>>>> <antoine.zimmermann@insa-lyon.fr
>>>>> <mailto:antoine.zimmermann@insa-lyon.fr>> wrote:
>>>>>
>>>>> Dear all,
>>>>>
>>>>>
>>>>> I'm looking for scientific publications related to OWL Full. I'm
>>>>> interested in the following kind of work:
>>>>> - reasoning with OWL Full;
>>>>> - modelling ontologies in OWL Full;
>>>>> - properties of OWL Full, or relationships between OWL Full and
>>>>> other formalisms.
>>>>>
>>>>> I've found some papers about modelling existing ontologies in OWL
>>>>> (for instance, modelling a UML spec or a frame-based ontology in
>>>>> OWL) which happen to fall into OWL Full, but nothing about modelling
>>>>> OWL Full ontologies by design. I found very little about reasoning
>>>>> in OWL Full (with the notable exception of [1], which also relates
>>>>> OWL reasoning to OOP).
>>>>> But the vast majority of papers mentioning OWL Full present it as
>>>>> the language that must be avoided at all cost (usually saying "if we
>>>>> do that, we are in OWL Full" implying "if we do that, we're screwed!").
>>>>>
>>>>> Thanks in advance for your pointers.
>>>>>
>>>>>
>>>>> [1] Seiji Koide and Hideaki Takeda. OWL-Full Reasoning from an
>>>>> Object Oriented Perspective. In R. Mizoguchi, Z. Shi, and F.
>>>>> Giunchiglia (Eds.): ASWC 2006, LNCS 4185, pp. 263–277, 2006.
>>>>> Springer-Verlag Berlin Heidelberg 2006.
>>>>>
>>>>>
>>>>> Regards,
>>>>> --
>>>>> Antoine Zimmermann
>>>>> Researcher at:
>>>>> Laboratoire d'InfoRmatique en Image et Systèmes d'information
>>>>> Database Group
>>>>> 7 Avenue Jean Capelle
>>>>> 69621 Villeurbanne Cedex
>>>>> France
>>>>> Tel: +33(0)4 72 43 61 74<tel:%2B33%280%294%2072%2043%2061%2074> -
>>>>> Fax: +33(0)4 72 43 87 13<tel:%2B33%280%294%2072%2043%2087%2013>
>>>>>
>>>>> Lecturer at:
>>>>> Institut National des Sciences Appliquées de Lyon
>>>>> 20 Avenue Albert Einstein
>>>>> 69621 Villeurbanne Cedex
>>>>> France
>>>>> antoine.zimmermann@insa-lyon.fr<mailto:
>>>>> antoine.zimmermann@insa-lyon.fr>
>>>>>
>>>>> http://zimmer.aprilfoolsreview.com/
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Michael Uschold, PhD
>>>>> Senior Ontology Consultant, Semantic Arts
>>>>> LinkedIn: http://tr.im/limfu
>>>>> Skype, Twitter: UscholdM
>>>>>
>>>>>
>>>>>
>>>> --
>>>> Dr. Markus Krötzsch
>>>> Oxford University Computing Laboratory
>>>> Room 306, Parks Road, Oxford, OX1 3QD, UK
>>>> +44 (0)1865 283529 http://korrekt.org/
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>
> --
> Dr. Markus Krötzsch
> Oxford  University  Computing  Laboratory
> Room 306, Parks Road, Oxford, OX1 3QD, UK
> +44 (0)1865 283529    http://korrekt.org/
>
>


-- 
Michael Uschold, PhD
   Senior Ontology Consultant, Semantic Arts
   LinkedIn: http://tr.im/limfu
   Skype, Twitter: UscholdM