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Re: RE : RE : RE : RE : Suggestion for SKOS FAQ

From: Andreas Langegger <al@jku.at>
Date: Tue, 18 Mar 2008 22:58:34 +0100
To: "Sini, Margherita (KCEW)" <Margherita.Sini@fao.org>
Message-Id: <0D1A7BA7-8AFF-40E5-BF18-93F88F6B0E31@jku.at>
Cc: Antoine Isaac <Antoine.Isaac@KB.nl>, SKOS <public-esw-thes@w3.org>

yes. I think this is not possible, because the application or user can  
always select triples or execute queries referring to  
skos:transitiveBroader which will result in the transitivity (this one  
which is ment "for free" ;-) but in some cases may be forbidden)

so, that's why skos:broaderIntransitive was suggested earlier in this  
thread I guess...

regards
Andy


On Mar 18, 2008, at 5:55 PM, Sini, Margherita (KCEW) wrote:

> Dear all,
>
> I understood the point explained by Stella and I agree.
>
> But i would like to return to the proposal to make  
> skos:broaderTransitive a
> super-property of skos:broader.
>
> I understood the point of Alistar that it is possible to have non- 
> transitive
> sub-properties of transitive properties and viceversa. I agree on  
> that.     I
> also clarify on my mind inheritance.
>
> But:  what if i would like to express:
> A skos:broader B
> B skos:broader C
> and assert that A not-skos:broader C?
>
> in other words i would like to express intransitivity. How do i do  
> that?
>
> Also: is this topic associated to some issue? maybe issue 44 or  
> there is a
> more specific one?
>
> Thanks
> Margherita
>
> 	-----Original Message-----
> 	From: public-esw-thes-request@w3.org on behalf of Antoine Isaac
> 	Sent: Fri 3/14/2008 11:26
> 	To: al@jku.at; SKOS
> 	Cc:
> 	Subject: RE : RE : RE : RE : Suggestion for SKOS FAQ
> 	
> 	
>
>
> 	Dear Andy,
> 	
> 	>> Is there a current draft for the new SKOS core as rdf? I can only
> find
> 	this one which doesn't include the new transitivity solution:
> http://www.w3.org/2004/02/skos/core.rdf
> 	>>
> 	
> 	That's indeed an outdated one. There should be a new one by the time
> SKOS goes candidate recommendation, but for the moment there is  
> nothing
> available
> 	
> 	>>
> 	I assume skos:transitiveBroader is an owl:TransitiveProperty
> (http://www.w3.org/TR/owl-ref/#TransitiveProperty-def
> 	). If skos:broader is a sub property of skos:broaderTransitive this
> 	does not imply skos:broader is also an owl:TransitiveProperty! - it
> is
> 	no sub class it's just a sub property ;-)
> 	So, if I use the skos:whateverTransitive property e.g. in a SPARQL
> 	query, I get the whole transitive closure of the concept relation and
> if I use skos:broader/etc. I only get direct assertions, right? With
> 	this approach it's possible to interpret relations as transitive by a
> query/application although the author of the KOS did not even use
> 	transitive properties, right? That's fine ;-)
> 	>>
> 	
> 	That's *exactly* this!
> 	
> 	Cheers,
> 	
> 	Antoine
> 	
> 	Thanks,
> 	Andy
> 	
> 	On Mar 13, 2008, at 1:51 PM, Antoine Isaac wrote:
> 	
> 	> I'm sorry I don't have time to read all your mail and answer point
> 	> by point.
> 	>
> 	> But it seems really related to confusion about transitivity and
> 	> inheritance.
> 	> You indeed assume that if something is transitive, then it has more
>> information defined, and thus should be a sub-property of a non-
> 	> transitive property.
> 	>
> 	> But it is prefectly possible to say that a superproperty is
> 	> transitive. That says something about its graph (that is, the
> 	> couples (x,y) that are related by the property, as the As and Bs in
>> your example).
> 	> But now, if you have a sub-property, formally it is defined as a
> sub-
> 	> part of the graph. So you lose elements (couples), and something
> 	> that was true at the level of the super-property (e.g.
> transitivity)
> 	> might not be true anymore for the sub-property.
> 	>
> 	> Example:
> 	> - one property 'blob1' defined by the graph {(a,b), (b,c), (a,c)}
> 	> (it relates only these elements) is transitive
> 	> - one property 'blob2' defined by the graph {(a,b), (b,c)}
> 	> blob2 is a sub-property of blob1 and yet blob2 is not transitive.
> 	>
> 	> That's what happens currently in SKOS, where blob1 is
> 	> broaderTransitive and blob2 is broader
> 	>
> 	> Antoine
> 	>
> 	>
> 	> -------- Message d'origine--------
> 	> De: Sini, Margherita (KCEW) [mailto:Margherita.Sini@fao.org]
> 	> Date: jeu. 13/03/2008 09:05
> 	> └: Antoine Isaac; Stephen Bounds; SKOS
> 	> Cc: al@jku.at
> 	> Objet : RE: RE : RE : Suggestion for SKOS FAQ
> 	>
> 	> Dear all,
> 	>
> 	> I appreciate the efforts from Alistar, Stephen and Simon to explain
>> this, but
> 	> (sorry) unfortunately I am not convinced.. maybe I miss
> something....
> 	> Let me summarize from my point of view so that you can tell me if I
>> am wrong:
> 	>
> 	> - we say that for skos:broader we could not say if it is transitive
> or
> 	> intransitive (it may be or not be = could be locally transitive but
>> could be
> 	> also not transitive).
> 	> - we say that if somebody want to say that they broader
> 	> relationships is
> 	> really transitive, can use a specific one "broaderTransitive"
> 	> - I think that in OWL, when we say subclassof we actually means "is
> A"
> 	>
> 	> So this situation:
> 	>
> 	> skos:semanticRelation
> 	>   skos:broaderTransitive
> 	>     skos:broader
> 	>
> 	>   A skos:broader B
> 	>   B skos:broader C
> 	>
> 	> means also:
> 	>
> 	> 1)   skos:broader "isA" skos:broaderTransitive which I think is not
>> what we
> 	> want...
> 	>
> 	> 2) We get the transitivity for free:
> 	>
> 	>   A skos:broaderTransitive B
> 	>   B skos:broaderTransitive C
> 	> therefore
> 	>   A skos:broaderTransitive C
> 	>
> 	> ... But what about if I wanted to say that
> 	>
> 	>   A skos:broader B
> 	>   B skos:broader C
> 	>
> 	> and they are not transitive?
> 	>
> 	> I think that if somebody wanted the trasitivity NEEDED to
> 	> *explicitly assert*
> 	> statements ... otherwise we assume that all skos:broader are also
> 	> skos:broaderTransitive, no?
> 	>
> 	> Then we have:
> 	>
> 	> - super-properties make *less* restrictive statements about the
> world.
> 	> skos:broader I think is less restrictive than
> skos:broaderTransitive
> 	> because
> 	> as I understood "skos:broader" we not not know about Transitivity,
> but
> 	> "skos:broaderTransitive" IS transitive, so IT is more restrictive,
> no?
> 	>
> 	> Then we have:
> 	>
> 	> >>>We can't reverse the order of skos:broaderTransitive and
> 	> skos:broader in
> 	> the because of the transitive case.  If:
> 	> <<<
> 	>
> 	> skos:semanticRelation
> 	>   skos:broader
> 	>     skos:broaderTransitive
> 	>
> 	>    A skos:broaderTransitive B  and
> 	>    B skos:broaderTransitive C  then
> 	>    A skos:broaderTransitive C  but
> 	>
> 	>    A skos:broader C   YES because in this case we agreed that A and
>> B and B
> 	> and C are related by  transitite broader
> 	>
> 	>
> 	> Therefore I can propose another solution:
> 	>
> 	>   skos:semanticRelation
> 	>     skos:broader
> 	>       skos:broaderTransitive
> 	>       skos:broaderIntransitive
> 	>
> 	>    A skos:broaderTransitive B  and
> 	>    B skos:broaderTransitive C  then
> 	>    A skos:broaderTransitive C  but
> 	>    therefore A skos:broader C   --> is correct to arrive here
> 	>
> 	>    A1 skos:broaderIntransitive B1  and
> 	>    B1 skos:broaderIntransitive C1  then
> 	>    A1 and C1  are not related
> 	>    therefore we cannot say A1 skos:broader C1   which is correct to
>> arrive to
> 	> this conclusion because we agreed that A1 is broader than B1 and b1
>> broader
> 	> than C1 but in an intransitivity way...
> 	>
> 	> Where I am wrong?
> 	> Thanks
> 	> Margherita
> 	>
> 	>
> 	> -----Original Message-----
> 	> From: Antoine Isaac [mailto:Antoine.Isaac@KB.nl]
> 	> Sent: 12 March 2008 13:09
> 	> To: Stephen Bounds; SKOS
> 	> Cc: Sini, Margherita (KCEW); al@jku.at
> 	> Subject: RE : RE : Suggestion for SKOS FAQ
> 	>
> 	>
> 	> Thanks a lot Stephen for your clarification.
> 	>
> 	> I would actually add: at some point we considered in the WG (and I
> was
> 	> supporting this) that broaderTransitive could be actually a
> 	> subproperty of
> 	> skos:broader.
> 	>
> 	> This actually would have matched cases for which you allow
> 	> skos:broader to be
> 	> locally transitive (that is, on certain KOSs and not on others),
> 	> which is
> 	> what we wanted (and still allow, on the condition that KOS creators
> 	> explicitly assert the 'extra' A skos:broader C -kind of links).
> 	>
> 	> But this was judged less convenient. Because then if you want to
> say
> 	> that the
> 	> broaders of a given KOS are transitive, you have to *explicitly
> 	> assert*
> 	> statements of broaderTransitive.
> 	>
> 	> While with the current version, you get the transitivity for free:
> 	> whenever
> 	> you assert a broader, there is a transitive one that is inferred
> for
> 	> it, de
> 	> facto building a transitive hierarchy for your KOS. Meanwhile, you
> 	> can still
> 	> access your original skos:broader statements, without having them
> 	> messed up
> 	> by the transitivity.
> 	>
> 	> Antoine
> 	>
> 	>
> 	> -------- Message d'origine--------
> 	> De: public-esw-thes-request@w3.org de la part de Stephen Bounds
> 	> Date: mar. 11/03/2008 22:39
> 	> └: SKOS
> 	> Cc: Sini, Margherita (KCEW); al@jku.at
> 	> Objet : Re: RE : Suggestion for SKOS FAQ
> 	>
> 	>
> 	> Hi Margaret & Andy,
> 	>
> 	> I thought that too when I first looked at the SKOS Primer, but you
> 	> need
> 	> to remember that OWL sub-properties are subtractive, not additive.
> 	>
> 	> Another way of putting this is that super-properties make *less*
> 	> restrictive statements about the world.
> 	>
> 	> The full hierarchy of skos:broader is:
> 	>
> 	>   skos:semanticRelation
> 	>    skos:broaderTransitive
> 	>     skos:broader
> 	>
> 	> Which means that for A skos:broader B, this entails that:
> 	>
> 	>   A skos:broaderTransitive B  and
> 	>   A skos:semanticRelation B
> 	>
> 	> We can't reverse the order of skos:broaderTransitive and
> 	> skos:broader in
> 	> the because of the transitive case.  If:
> 	>
> 	>    A skos:broaderTransitive B  and
> 	>    B skos:broaderTransitive C  then
> 	>    A skos:broaderTransitive C  but
> 	>
> 	>    A skos:broader C   is NOT entailed
> 	>
> 	> If skos:broader were a super-property of skos:broaderTransitive,
> this
> 	> statement would also need to be true.
> 	>
> 	> Regards,
> 	>
> 	> -- Stephen.
> 	>
> 	> Sini, Margherita (KCEW) wrote:
> 	> > I agree with Andy, I also think it should be a sub-property, not
> a
> 	> > super-property...
> 	> >
> 	> > Regards
> 	> > Margherita
> 	> >
> 	> >     -----Original Message-----
> 	> >     *From:* public-esw-thes-request@w3.org
> 	> >     [mailto:public-esw-thes-request@w3.org] *On Behalf Of
> *Andreas
> 	> Langegger
> 	> >     *Sent:* 11 March 2008 12:14
> 	> >     *To:* Alasdair J G Gray
> 	> >     *Cc:* Antoine Isaac; Simon Spero; iperez@babel.ls.fi.upm.es;
> 	> SKOS
> 	> >     *Subject:* Re: RE : Suggestion for SKOS FAQ
> 	> >
> 	> >     Hi,
> 	> >
> 	> >     first I din't pay much attention to your discussion, because
> I
> 	> >     thought this case is clear... looking at the spec I read
> 	> >     "skos:broaderTransitive owl:subClassOf skos:broader" - but
> 	> there it
> 	> >     says (to my surprise): skos:broaderTransitive and others are
> 	> "super
> 	> >     properties" - why that?
> 	> >
> 	> >     If I would model this I would say:
> 	> >
> 	> >     skos:semanticRelation a owl:ObjectProperty .
> 	> >     skos:broader a skos:semanticRelation .
> 	> >     skos:narrower a skos:semanticRelation .
> 	> >     skos:broaderTransitive a skos:broader; a
> 	> owl:TransitiveProperty .
> 	> >     skos:narrowerTrasnsitive a skos:narrower; a
> 	> owl:TransitiveProperty .
> 	> >     and so on...
> 	> >
> 	> >     can anybody comment on this why the specs says "super
> 	> property" and
> 	> >     not "sub property" ?
> 	> >     Whith the statements above I can deceide whether to allow
> 	> >     transitivity or not. And because of OWA, skos:broader not
> 	> explicitly
> 	> >     asserted as a transtive property, it does not mean, that it
> 	> _cannot
> 	> >     be_ transitive, sure it can, but it does not need to be
> valid.
> 	> >
> 	> >     If a taxonomy should be ISO2788 compliant, just use the
> 	> *Transitive
> 	> >     versions - so it's up to the modeler and not to the
> application
> 	> >     which I think is fine.
> 	> >
> 	> >     regards
> 	> >     Andy
> 	>
> 	>
> 	
> 	
> 	
> ----------------------------------------------------------------------
> 	Dipl.-Ing.(FH) Andreas Langegger
> 	Institute for Applied Knowledge Processing
> 	Johannes Kepler University Linz
> 	A-4040 Linz, Altenberger Stra▀e 69
> 	http://www.langegger.at <http://www.langegger.at/>
> 	
> 	
> 	
>


----------------------------------------------------------------------
Dipl.-Ing.(FH) Andreas Langegger
Institute for Applied Knowledge Processing
Johannes Kepler University Linz
A-4040 Linz, Altenberger Stra▀e 69
http://www.langegger.at
Received on Tuesday, 18 March 2008 21:59:53 GMT

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