Re: doubt about "Synset / Concept" class

Dear all,

I subscribe Philipp's arguments completely. SKOS data model is an OWL
Full ontology and their concepts can be owl instances and/or classes
depending on the circumstances and, as such, could be subject of a
lexical realisation in a lemon/ontolex lexicon. I do not see why not,
or why they should be treated differently.

> [John:] Informal representations are not really the focus of the group ...

I wouldn't say that SKOS models are "informal", rather they can be
considered "semi-formal". And, is the dbpedia dataset a "formal"
knowledge representation even if it is written in rdf/owl? I am not so
sure ;-)

Regards,
Jorge


2013/5/8 John McCrae <jmccrae@cit-ec.uni-bielefeld.de>:
> 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
>
> Normalize token and identify lexical entry
> For each sense
>
> If there is a ontolex:reference yield its object
> For each ontolex:means (following all skos:exactMatchs thereafter) yield the
> object of ontolex:conceptualizes of this object
>
> 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" 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
>>>>> > Fax: +49 521 106 12412
>>>>> > 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
>>
>>
>



-- 
Jorge Gracia, PhD
Ontology Engineering Group
Artificial Intelligence Department
Universidad Politécnica de Madrid
http://delicias.dia.fi.upm.es/~jgracia/

Received on Thursday, 9 May 2013 00:02:26 UTC