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RE: identity of SKOSXL labels

From: Armando Stellato <stellato@info.uniroma2.it>
Date: Sat, 4 Jan 2014 19:01:10 +0100
To: "'Antoine Isaac'" <aisaac@few.vu.nl>
Cc: <public-esw-thes@w3.org>
Message-ID: <042001cf0976$f38515d0$da8f4170$@info.uniroma2.it>
Dear Antoine,

many thanks for your further reply.
No need to be afraid of anything, actually your answer is complete as it represents the current situation: there is no enforcement by SKOSXL and it's a modeler's choice. 
I really had this doubt as I just remembered to have read something about the fact that SKOSXL labels should not be considered as independent lexical objects, thus hinting at the fact that any concept *should* actually have their own labels. But maybe it was just a paper on proposals and not a definitive word on the matter.

Thanks again, I'll behave accordingly for the two cases I presented. 

Cheers,

Armando

> -----Original Message-----
> From: Antoine Isaac [mailto:aisaac@few.vu.nl]
> Sent: Saturday, January 4, 2014 10:40 AM
> To: Armando Stellato
> Cc: public-esw-thes@w3.org
> Subject: Re: identity of SKOSXL labels
> 
> Hello Armando,
> 
> Sorry for having missed the other part of your question.
> 
> I'm afraid I can't give you a complete answer however: to some extent it
> depends on the nature of the knowledge/lexical system you want to
> represent in SKOS.
> 
> Imagine "foo" is the label you want to link to C1 and C2. Can this label get a
> different set of attributes, when it is linked to C1 or C2? If not, then creating
> and re-using one same URI (ex:foo) makes sense. Otherwise, if you think
> "foo" may get different properties depending on its context of use, then you
> must create two uris ex:foo-C1 and ex:foo-C2.
> 
> I'm sorry not to give a more precise answer. The truth is, that at the time we
> thought of SKOS-XL constraints, we foresaw both kinds of scenarios, and one
> did not seem more legitimate for us to enforce/support it.
> 
> Best,
> 
> Antoine
> 
> On 1/4/14 2:57 AM, Armando Stellato wrote:
> > Dear Antoine,
> >
> > thanks a lot for the detailed background on it, it is really appreciated, as I
> get more of the design principles behind SKOS/SKOSXL.
> > However - and I hope not to be annoying - this clarifies things on one side
> (the "what if" with existing labels), while still leaving some doubt on the
> other (how to create labels).
> >
> > What I am asking is, with reference to the examples I made in my first
> email:
> > If I have to create skosxl:labels for concepts C1 and C2 (with identical literal
> form "foo"), and if I'm willing to use URIs (not bnodes), should I create them
> with *different* URIs? (is SKOSXL enforcing this? Is it a best practice? Is it
> suggested but not mandatory?).
> >
> > The "identity is not guaranteed" statement with respect to skosxl:labels
> with identical literalForms is clear to me, but formally, it does not entail an
> answer to my question above (because it may hold to be true for very
> different answers to that question).
> >
> > Many thanks,
> >
> > Armando
> >
> >> -----Original Message-----
> >> From: Antoine Isaac [mailto:aisaac@few.vu.nl]
> >> Sent: Thursday, January 2, 2014 9:39 PM
> >> To: public-esw-thes@w3.org
> >> Subject: Re: identity of SKOSXL labels
> >>
> >> Dear Armando,
> >>
> >> In SKOS-XL if two instances of xl:Label have the same literalForm,
> >> then it does *not* follow that they are the same resource.
> >>
> >> This was in fact the subject of a lot of discussions in the making of
> >> SKOS. We investigated quite in depth the alternatives, but couldn't
> >> come with a strong motivation for coming with an 'identity rule'. In
> >> fact it seems dangerous to enforce identify of resources from identity of
> literalForm.
> >>
> >> Quoting this year's paper on the design of SKOS:
> >> (http://dx.doi.org/10.1016/j.websem.2013.05.001)
> >> [
> >> Two concerns that arose during discussions of modeling alternatives
> >> for label relations were: identity conditions (When are two instances
> >> of the class skosxl:Label the same individual?), and the formal
> >> relationship between the class skosxl:Label and the set of RDF plain
> >> literals (Can instances of the class skosxl:Label have more than one
> >> literal form?). The working group decided to assert that instances of
> >> skosxl:Label have exactly one literal form in order to avoid
> >> ambiguity, but that sharing a common literal form should not be
> >> sufficient to infer that two instances of the class skosxl:Label were
> >> the same individual. In other words, two distinct instances of
> >> skosxl:Label might have the same literal form; there is no one-to-one
> mapping between the class extension of skosxl:Label and the set of RDF plain
> literals.
> >> ]
> >>
> >> I don't remember all the arguments then. But one was clearly that the
> >> identity rule could harm interoperability with the kind of
> >> ontology-lexicon models you're refering to. When mapping these models
> >> to SKOS(-XL), it may make sense to represent as different resources
> >> two lexicon entries that would have a same literal form. For example for a
> words that is polysemous.
> >> I'm not saying that this should be the reference representation of
> >> such models in SKOS-XL, but we certainly didn't want to forbid such
> scenarios!
> >>
> >> Also, from a pragmatic perspective, having the identity rule would
> >> have made xl:Label really close from being a reified version of
> >> rdfs:Literal. I.e., it would have practically allowed a trick to have
> >> literals as subject of statements). This might have had some
> >> consequences stretching quite far away the group's original mandate
> >> (representing KOSs in a basic way, not offering alternative to low-level
> RDF representation issues).
> >>
> >> Cheers,
> >>
> >> Antoine
> >>
> >> On 1/2/14 8:05 PM, Armando Stellato wrote:
> >>> Hi Johan,
> >>>
> >>> yes my bad I forgot to mention also the Appendix B of skos core,
> >>> which I
> >> already read in the past, and in fact much of the doubts remain.
> >>>
> >>> By re-reading that section, I may confirm that it is not guaranteed
> >>> that,
> >> given two skosxl:Labels with the same literalForm, these are the same
> >> resource.
> >>>
> >>> However, this “is not guaranteed” does not allow me to infer at all
> >>> if
> >> SKOSXL enforces that C1 and C2 **should** have their own distinct
> >> labels, or if different modeling choices may allow the same URI to be
> >> used for labels with same literal form belonging to different
> >> concepts. The question is if, though reified, in a certain sense, the
> >> label remains “an appendix of the concept” or has (may have) a life of its
> own.
> >>>
> >>> The request may seem fussy, but here are two scenarios for which it
> >>> is
> >> important to determine the above:
> >>>
> >>> 1)Compatibility with ontology-lexicon models, such as the one being
> >> developed here: http://www.w3.org/community/ontolex/
> >>> Clearly, if same entries from a lexicon can be attached to more
> >>> concepts,
> >> such models would be totally incompatible (not possible to specify
> >> rdfs:subClassOf rels) with skosxl:Label, in the case that
> >> skosxl:Labels have to be unique for each concept (i.e. even when
> >> others with the same literalForm already exist)
> >>>
> >>> 2)SKOSXL development tools (such as http://vocbench.uniroma2.it/).
> >> Which sort of integrity checks (out of the owl reasoning) should be
> >> made while a skosxl:label is being created? Should different
> >> “modalities” be selectable, or is there a clear design rule/best practice?
> >>>
> >>> Cheers,
> >>>
> >>> Armando
> >>>
> >>> *From:*Johan De Smedt [mailto:johan.de-smedt@tenforce.com]
> >>> *Sent:* Thursday, January 2, 2014 2:47 PM
> >>> *To:* 'Armando Stellato'; public-esw-thes@w3.org
> >>> *Subject:* RE: identity of SKOSXL labels
> >>>
> >>> Hi Armando,
> >>>
> >>> You may want to have a look at the SKOS reference -
> >> http://www.w3.org/TR/skos-reference/#xl
> >>>
> >>> In particular Section B.2.4.1 (and less relevant for your issue:
> >>> B.3.4.2)
> >>>
> >>> Kind Regards,
> >>>
> >>> *Johan De Smedt *
> >>>
> >>> /Chief Technology Officer/
> >>>
> >>> //
> >>>
> >>> mail: johan.de-smedt@tenforce.com <mailto:johan.de-
> >> smedt@tenforce.com>
> >>>
> >>> mobile: +32 477 475934
> >>>
> >>> mail-TenForce
> >>>
> >>> *From:*Armando Stellato [mailto:stellato75@gmail.com] *On Behalf Of
> >> *Armando Stellato
> >>> *Sent:* Thursday, 02 January, 2014 13:46
> >>> *To:* public-esw-thes@w3.org <mailto:public-esw-thes@w3.org>
> >>> *Subject:* identity of SKOSXL labels
> >>>
> >>> Dear all,
> >>>
> >>> suppose in SKOS I have:
> >>>
> >>> mythes:C1  skos:prefLabel “foo”
> >>>
> >>> mythes:C2  skos:altLabel “foo”
> >>>
> >>> In SKOSXL, should I have something like:
> >>>
> >>> mythes:C1  skosxl:prefLabel mythes:foo
> >>>
> >>> mythes:C2  skosxl:altLabel mythes:foo
> >>>
> >>> mythes:foo skosxl:literalForm “foo”
> >>>
> >>> or like this? :
> >>>
> >>> mythes:C1  skosxl:prefLabel mythes:foo_1
> >>>
> >>> mythes:C2  skosxl:altLabel mythes:foo_2
> >>>
> >>> mythes:foo_1 skosxl:literalForm “foo”
> >>>
> >>> mythes:foo_2 skosxl:literalForm “foo”
> >>>
> >>> in other words, is SKOSXL enforcing in any way that concepts which
> >>> are
> >> expressed through same lexicals, should have in any case their own
> >> labels for them or, on the contrary, a same label should be used…or
> >> these is no indication about that?
> >>>
> >>> In http://www.w3.org/TR/skos-reference/skos-xl.htmlthere is no hint
> >> about that, but I almost recall that I read/heard somewhere that the
> >> skosxl reification of the labels is *not* meant to “unify” labels
> >> with identical literalForms under a same URI, thus the general rule
> >> is to use in any case a different label URI for each concept.
> >>>
> >>> Could anyone shed some light on this? (and, in case, point me to the
> >> appropriate link if there is any…)
> >>>
> >>> Cheers,
> >>>
> >>> Armando
> >>>
> >>> P.S: in the example, I put a prefLabel for C1  and an altLabel for
> >>> C2, but
> >> assuming the specific properties being used do not affect the answer
> >> to my question, so it could be skos:***Label. Pls let me know if this
> >> matters anyhow.
> >>>
> >
> >
Received on Saturday, 4 January 2014 18:01:43 UTC

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