Re: doubt about "Synset / Concept" class

Hi,

The point is not the SKOS doesn't have an RDF-OWL semantics, of course it
does! Actually, so does *lemon, *thus by that reasoning every property in
the entire *lemon* model could be replaced with lemon:reference and
everything would be much less confusing![/sarcasm]

In fact we care about whether the intension/extension of the SKOS concept
is the same as inferred by the OWL reasoner. In my cat example it was not,
I intended to express the concept of a cat but was left inferring only the
genus to which cats belong.

This matters a lot to us, as we want to be able to provide a mapping to and
from a lexical expression and its formal representation. SKOS is not formal:

To understand this distinction, consider that the "knowledge" made explicit
> in a formal ontology is expressed as sets of axioms and facts. A thesaurus
> or classification scheme is of a completely different nature, and does not
> assert any axioms or facts. --
> http://www.w3.org/TR/2009/REC-skos-reference-20090818/


The SKOS model may be defined by an OWL ontology, but a model expressed
using SKOS is not an ontology! It is of a completely different nature, a
informal representation of meaning.

Informal representations are not really the focus of the group other than
as a bridge to getting to formal representation (i.e., via WordNet
synsets). More practically, this is because non-formal schemes lack
fundamental elements (like valence which is very important here
http://www.w3.org/community/ontolex/wiki/Specification_of_Requirements/Valence_and_Ontological_Mapping
).*

To illustrate this consider the case of a word sense disambiguation
algorithm based on OWL reasoning, in model 2 it would work as follows

   1. Normalize token and identify lexical entry
   2. For each sense
      1. If there is a ontolex:reference yield its object
      2. For each ontolex:means (following all skos:exactMatchs thereafter)
      yield the object of ontolex:conceptualizes of this object
   3. Apply OWL reasoning to select best ontology entity

In model 1, it becomes more ambiguous: not every ontolex:reference yields
an ontology entity and more importantly it is not clear which do.

While I don't think that the difference is humongously important, I would
say that the OntoLex group should focus on how we link ontologies to
lexica, if we link ontologies to lexica via KOS/terminologies that may be a
necessary evil (by which I of course mean a very important and useful use
case). Our goal is not to be KOSLex or TermLex: but if we can do it neatly
as a by-product, that's good. As for confusing people, we will only
confuses people who do not understand/care about the difference between
formal/informal semantic models, therefore I view using two properties as a
zero-less strategy, people who care about the difference will get it right
(because they care and from my experience there are many who do) and people
who don't care will choose at random but it doesn't matter as their model
is a mish-mash of formal and informal declarations anyway as they don't
care (which again many "SKOS
ontologies<http://scholar.google.de/scholar?hl=en&q=%22skos+ontology%22>"
are)... and if we are very lucky some people, who don't care very much,
will care just enough to read the documentation!

Regards,
John

* Caveat: SKOS is not the best example as it does provide some formal
description, e.g., transitiveBroader along side non-formal description,
e.g., broader




On Wed, May 8, 2013 at 10:39 PM, Aldo Gangemi <aldo.gangemi@cnr.it> wrote:

> Uhm, you're talking of two different things here.
> Indeed SKOS in RDF-OWL has a semantics (intensional and extensional), but
> this is true also for WordNet synsets, senses and words, as well as for any
> other datum encoded in RDF-OWL. For that reason should we then use only
> ontolex:reference for everything?
> And I also see that subtle distinctions can be hard to digest to
> non-experts. But no distinctions at all is an even worse problem. With the
> design rationale that any OWL individual can be used as a reference *in
> general* (in particular cases is of course perfectly fine to treat them all
> as references), nothing can justify why SKOS concepts are ok and others not.
> I see two escapes:
>
> 1) we maintain the suggestion to use skos:exactMatch for mapping to SKOS,
> explaining why and how, as it's common in design patterns for software,
> ontologies, and data (people like being explained useful things sometimes
> ;))
> 2) we collapse the properties, but we create an OWL axiom that states e.g.
> the following general class axiom:
> (ontolex:reference some skos:Concept) owl:equivalentTo (skos:exactMatch
> some skos:Concept)
>
> Aldo
>
> On May 8, 2013, at 4:52:54 PM , Philipp Cimiano <
> cimiano@cit-ec.uni-bielefeld.de> wrote:
>
>  John,
>
> of course skos:Concepts have a formal interpretation and thus an extension
> much as owl:Classes.
>
> So I am not assuming:
>
> :cat rdf:type skos:Concept ⊨ :cat rdf:type owl:Thing
>
> But a SKOS document is an RDF document and thus has an RDF Interpretation
> which also assign denotations to the URIs in the document.
>
> Further, of course SKOS documents has a semantics, which is defined in OWL.
>
> For example skos:transitiverBroader is defined as a OWL transitive
> property.
>
> And btw. skos:Concept is defined as being an owl:Class, i.e. skos:Concept
> rdf:type owl:Class (see axiom S1 in
> http://www.w3.org/TR/2009/REC-skos-reference-20090818/)
>
> So SKOS is as axiomatized as any other OWL ontology ;-)
>
> So we should not treat SKOS concept as being really different from OWL
> concepts at the lexicon level. Such distinctions are very subtle and people
> will not grasp this difference, having doubts on which property to use in a
> particular case. This will compromise the usability of the model IMHO
>
> Philipp.
>
> Am 08.05.13 21:36, schrieb John McCrae:
>
>
>
>
> On Wed, May 8, 2013 at 5:56 PM, Philipp Cimiano <
> cimiano@cit-ec.uni-bielefeld.de> wrote:
>
>>  Dear all,
>>
>>     I am not with Aldo and John here.
>>
>> I think introducing two different properties makes our model
>> unnecessarily complex.
>>
>
>  Neither model introduces any new properties, the first allows reference
> to have two domains (skos:Concept and owl:Thing) but means only one
> (skos:Concept). The second model uses skos:exactMatch for matching within a
> SKOS model and differentiates reference  and means by domain (owl:Thing and
> skos:Concept respectively).
>
>
>>  We said we use "reference" when the meaning is expressed by an
>> extensional entity where we defined extensional as "having an extension in
>> some model of the theory". I agreed to that.
>>
>> According to this, a particular skos:Concept (an individual) has as much
>> as an extensional interpretation as a particular owl:Class, or an
>> owl:Individual to stay at the same level.
>>
> Eh? You are saying: "SKOS concepts have an extension in some model of the
> theory". This seems very odd, SKOS does not have any formal semantics,
> therefore how can it have models and extensions? The reasoning seems
> circular, if I assume SKOS concepts have extensions like an OWL entity then
> SKOS concepts are like OWL entities because they have extensions.
>
>>
>> Of course, a particular skos:Concept is an individual from an RDF/OWL
>> perspective and is also interpreted as some individual in the corresponding
>> domain, much like an owl:Individual. So a model assigns some extensional
>> interpretation to both skos:Concepts and owl:Individuals. Where is then the
>> essential difference that prevents us using the same property for both then?
>>
> Again, you are assuming that as
>
>  :cat rdf:type skos:Concept ⊨ :cat rdf:type owl:Thing
>
>  Ergo, :cat has an extension in OWL. But this only true because you
> applied an OWL reasoner, and more importantly the meaning has changed: the
> OWL reasoner has only indicated that there are is a (individual) thing (the
> genus of cats), where as the SKOS concept intended an extension as the
> class of cats.
>
>
>>
>> Surely, skos:Concept are per definition "intensions", but technically
>> they are extensional entities according to our definition, i.e.
>> owl:Individual or rdf:Thing.
>>
>> Further, it is perfectly fine for a skos:Concept to be an owl:Class (see
>> http://www.w3.org/TR/2009/REC-skos-reference-20090818/)
>>
>
>  True, but more importantly a skos:Concept can also be an
> owl:DatatypeProperty, an owl:ObjectProperty and an owl:Thing. The
> difference is the underspecification.
>
>
>> What do we use then? "reference" or "means"? ;-)
>>
>>
>> Treating skos:Concept and owl:Class as different types of meaning seems
>> too subtle for people who want to use the model in practice as they will
>> always wonder which is the right property to use.
>>
>
>  Regards,
> John
>
>
>> Philipp.
>>
>> Am 08.05.13 13:08, schrieb John McCrae:
>>
>> Hi Aldo,
>>
>>  Names in the previous example are not fixed of course. I also don't
>> like "means" that much I just haven't got a better alternative yet. (synset
>> is too WordNet-specific, means/meaning/concept are too broad)
>>
>>  Regards,
>> John
>>
>>
>> On Wed, May 8, 2013 at 1:02 PM, Aldo Gangemi <aldo.gangemi@cnr.it> wrote:
>>
>>>  Hi, I agree with John, we really seem on the same wave now :), in fact
>>> I agree with Model 2 being far better.
>>> Only, should we really use ontolex:means to link senses and synsets?
>>> It's a bit too broad as a name for a specific relation like that, isn't it?
>>>
>>>  Aldo
>>>
>>>  On May 8, 2013, at 6:37:22 AM , John McCrae <
>>> jmccrae@cit-ec.uni-bielefeld.de> wrote:
>>>
>>>  Hi Jorge, all,
>>>
>>>  Thanks for your comment, I agree this is an issue we should discuss. I
>>> think that it is clearly wrong to continue to treat skos:Concepts as
>>> ontological elements, they aren't and we shouldn't really confuse them. The
>>> question of whether we should still use SKOS terminologies as systems of
>>> reference for the model also seems clear to me (of course we should).
>>>
>>>  The question then boils down to this essential question: do we use the
>>> same property to reference both a skos:Concept and an ontology entity?
>>>
>>>  This leads to two variation on the model:
>>>
>>>  Model 1. (Same property)
>>>
>>>  With synsets
>>>
>>>  :corn --ontolex:sense-> :corn_sense1 --ontolex:means->
>>> wordnet:corn_n_xxx *--ontolex:conceptualizes->* fao:Corn (a
>>> skos:Concept)
>>> :corn --ontolex:sense-> :corn_sense1 --ontolex:means->
>>> wordnet:corn_n_xxx --ontolex:conceptualizes-> dbpedia:Corn (a owl:Class)
>>>
>>>  Without synsets
>>>
>>>  :corn --ontolex:sense-> :corn_sense1 *--ontolex:reference->* fao:Corn
>>> (a skos:Concept)
>>> :corn --ontolex:sense-> :corn_sense1 --ontolex:reference-> dbpedia:Corn
>>> (a owl:Class)
>>>
>>>  Model 2. (Different property)
>>>
>>>  With synsets
>>>
>>>  :corn --ontolex:sense-> :corn_sense1 --ontolex:means->
>>> wordnet:corn_n_xxx *--skos:exactMatch->* fao:Corn (a skos:Concept)
>>> :corn --ontolex:sense-> :corn_sense1 --ontolex:means->
>>> wordnet:corn_n_xxx --ontolex:conceptualizes-> dbpedia:Corn (a owl:Class)
>>>
>>>  Without synsets
>>>
>>>  :corn --ontolex:sense-> :corn_sense1 *--ontolex:means->* fao:Corn (a
>>> skos:Concept)
>>> :corn --ontolex:sense-> :corn_sense1 --ontolex:reference-> dbpedia:Corn
>>> (a owl:Class)
>>>
>>>  With further linking valid of
>>>
>>>  fao:Corn --ontolex:conceptualizes-> dbpedia:Corn
>>>
>>>
>>>  I prefer model two as it makes a clearer distinction between
>>> terminologies and ontologies, doesn't require linking two SKOS concepts
>>> with an ontolex property (which we should avoid as it is not our job to fix
>>> SKOS) and allows us to define a natural property for linking terminologies
>>> to ontologies.
>>>
>>>  Regards,
>>> John
>>>
>>>
>>>
>>> On Fri, May 3, 2013 at 2:58 PM, Jorge Gracia <jgracia@fi.upm.es> wrote:
>>>
>>>> Dear Philipp, all
>>>>
>>>> I am not able to join the telco today, sorry. But let me to formulate
>>>> a quick question about John's model
>>>> http://www.w3.org/community/ontolex/wiki/File:John-modelling.png);
>>>> maybe you can treat it today.
>>>> Following the previous discussions I can understand the inclusion of
>>>> the new class "Synset / Concept". My doubt is: despite the fact that
>>>> skos concepts could be represented with this new class, can we
>>>> alternatively continuing treating skos concepts (of external skos
>>>> ontologies) as "ontology entities"? (as in the IFLA example presented
>>>> last week). For me this option is very natural, fully compliant with
>>>> R3 "semantics by reference" and we shouldn't lose it.
>>>>
>>>> Best regards,
>>>> Jorge
>>>>
>>>>
>>>> 2013/5/2 Philipp Cimiano <cimiano@cit-ec.uni-bielefeld.de>:
>>>> > Dear all,
>>>> >
>>>> >  this is a gentle reminder that we will have our regular ontolex telco
>>>> > tomorrow.
>>>> >
>>>> > I intend to discuss the model proposed by John on the basis of the
>>>> > contributions of all of you.
>>>> > I would like to see if there is a chance that we agree on this model
>>>> as a
>>>> > building block for the further work.
>>>> >
>>>> > Here is a link to the conference metadata including access details:
>>>> >
>>>> >
>>>> http://www.w3.org/community/ontolex/wiki/Teleconference,_2013.03.05,_15-16_pm_CET
>>>> >
>>>> > Best regards,
>>>> >
>>>> > Philipp.
>>>> >
>>>> > --
>>>> > Prof. Dr. Philipp Cimiano
>>>> > Semantic Computing Group
>>>> > Excellence Cluster - Cognitive Interaction Technology (CITEC)
>>>> > University of Bielefeld
>>>> >
>>>> > Phone: +49 521 106 12249 <%2B49%20521%20106%2012249>
>>>> > Fax: +49 521 106 12412 <%2B49%20521%20106%2012412>
>>>> > Mail: cimiano@cit-ec.uni-bielefeld.de
>>>> >
>>>> > Room H-127
>>>> > Morgenbreede 39
>>>> > 33615 Bielefeld
>>>> >
>>>> >
>>>>
>>>>
>>>>
>>>> --
>>>> Jorge Gracia, PhD
>>>> Ontology Engineering Group
>>>> Artificial Intelligence Department
>>>> Universidad Politécnica de Madrid
>>>> http://delicias.dia.fi.upm.es/~jgracia/
>>>>
>>>>
>>>
>>>
>>
>>
>> --
>> Prof. Dr. Philipp Cimiano
>> Semantic Computing Group
>> Excellence Cluster - Cognitive Interaction Technology (CITEC)
>> University of Bielefeld
>>
>> Phone: +49 521 106 12249
>> Fax: +49 521 106 12412
>> Mail: cimiano@cit-ec.uni-bielefeld.de
>>
>> Room H-127
>> Morgenbreede 39
>> 33615 Bielefeld
>>
>>
>
>
> --
> Prof. Dr. Philipp Cimiano
> Semantic Computing Group
> Excellence Cluster - Cognitive Interaction Technology (CITEC)
> University of Bielefeld
>
> Phone: +49 521 106 12249
> Fax: +49 521 106 12412
> Mail: cimiano@cit-ec.uni-bielefeld.de
>
> Room H-127
> Morgenbreede 39
> 33615 Bielefeld
>
>
>