- From: Jorge Gracia <jgracia@fi.upm.es>
- Date: Thu, 9 May 2013 02:01:41 +0200
- To: John McCrae <jmccrae@cit-ec.uni-bielefeld.de>
- Cc: Aldo Gangemi <aldo.gangemi@cnr.it>, Philipp Cimiano <cimiano@cit-ec.uni-bielefeld.de>, "public-ontolex@w3.org" <public-ontolex@w3.org>
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