Re: RDF-star vs Wikidata for modelling Richard Burton

Another aspect to consider is that plain triples such as 

:lizTaylor :married :richardBurton 

sometimes simply are unable to capture more complex situations such as the one we are discussing here. There are too many things one could about each marriage beyond this simple triple, and this is what makes the RDF* syntax choke a bit. 

I agree with Dan in saying that overloading simple binary relationships can rapidly backfire, and I agree with Peter that wikidata Statements and the systematic use of mainSnaks has its own elegance, since it represents everything as an n-ary relation to which any additional statement can be added. 

Of course, RDF already has a structure beyond simple binary relationships, named graphs, that can be usefully adopted in this case capturing 90% of the intended meaning: 

:marriage1 {
 :lizTaylor :married :richardBurton  
}
:marriage1 :year 1964; 
 :location :montreal. 

:marriage2 {
 :lizTaylor :married :richardBurton 
}
:marriage2 :year 1975; 
 :location :botswana. 

Since the two :married statements appear in separate graphs, they do not collapse into the same triple. 

Yet, because of the well-known issue of the open set of semantics for RDF 1.1 graphs, the two :marriage graphs can not be understood as stated or non-stated in an absolute way, and in particular it is not possible to represent them as non-stated in the clear and unambiguous way that RDF* allows for simple triples: 

<<:lizTaylor :married :richardBurton>> :year 1964. 
<<:lizTaylor :married :richardBurton>> :year 1975. 

This leaves a painful gap in RDF and shows lack of symmetry. And this is why I proposed this group to consider a transition path connecting non-asserted triples from RDF* to non-asserted named graphs in a yet-to-be-described model. Regardless of whether conjectures can be such a model (a model that I find has its own elegance, of course), I truly believe that some "RDF* graphs", in addition to "RDF* triples", are a thing to pursue. 

Ciao

Fabio

> On 6 Dec 2021, at 17:50, Dan Brickley <danbri@google.com> wrote:
> 
> 
> 
> On Sun, 5 Dec 2021, 21:48 Cox, Simon (L&W, Clayton), <Simon.Cox@csiro.au> wrote:
> Isn't this example just a modelling issue? 
> 
> Multiple marriages between the same two people are nevertheless still multiple marriages. 
> So if the history was described in a marriage-centric way rather than a person-centric way, then everything would be 'easy'.
> 
> So the lurking question is: when to give up on overloading simple binary relations with extra qualifiers? 
> 
> The appeal of having a "dumb downable" path to a basic binary relationship is appealing. But you could imagine some rules/ontology approach to inferring ?X marriedToOnceOrCurrently ?Y etc from details of several marriages. 
> 
> But the more down that road you go, the more the "simple graph database" folks will be skeptical
> 
> Dan
> 
> -----Original Message-----
> From: Peter Patel-Schneider <pfpschneider@gmail.com> 
> Sent: Saturday, 4 December, 2021 01:42
> To: thomas lörtsch <tl@rat.io>; public-rdf-star@w3.org
> Subject: RDF-star vs Wikidata for modelling Richard Burton
> 
> Although there is quite a bit about the Wikidata (actually Wikibase) data model that I disagree with, I don't think that it is fair to say that it is horrible.
> 
> As far as I can tell from
> https://www.mediawiki.org/wiki/Wikibase/DataModel, there is no ordering of the statements for an entity in Wikibase nor is there any ordering of the statements for a property of an entity in Wikibase.  The ordering that one sees on Wikidata pages is simply an artifact of the display.  Although there may be some information in Wikidata that drives this ordering it is not representationally significant and can change without affecting the meaning of the data in Wikidata.  (Well, at least the information about Richard Burton, would not change simply because ordering in the display of his marriage information changes.)
> 
> Where Wikibase is different from RDF* is that there is no guarantee that there is only one statement (Wikibase's rough analogue of a
> triple) with a given entity (subject), mainSnak property (predicate), and mainSnak value (object).  This can be seen in Richard Burton's spouses where there are two statements with entity Richard Burton, mainSnak property spouse, and value Elizabeth Taylor.  My understanding is that having no auxiliary information (such as start and end times) associated with these two statements would be something that should be somehow fixed up, but as there are different start and end times for these two statements then everything is in order.
> 
> So this use case (marrying the same person more than once) works very well in Wikibase, but at the cost of potentially having what might be called duplicate triples.  Users of WIkidata should be aware of this possibility and arrange to do whatever their right thing is when they encounter this situation.
> 
> RDF* does not handle this nearly as well.  There is discussion on this very point in https://github.com/w3c/rdf-star/issues/36

> 
> Note that I'm not saying that the best way to model serial-monagamy- with-possibility-of-remarriage-to-the-same-person is via spouse statements.  I'm just saying that Wikibase can handle decorated spouse triples much better than RDF* can.  This use case provides an example where uniqueness hurts for more than just beliefs or provenance and shows that the :occurence solution has big problems.
> 
> peter
> 
> 
> On Fri, 2021-12-03 at 12:22 +0100, thomas lörtsch wrote:
> > 
> > 
> > Am 3. Dezember 2021 11:40:10 MEZ schrieb Pierre-Antoine Champin
> > <pierre-antoine.champin@ercim.eu>:
> > > On 03/12/2021 09:23, Dan Brickley wrote:
> > > 
> > > > Yes, nice and concrete!
> > > > 
> > > > What if Alice were Elizabeth Taylor, and Bob were Richard Burton
> > > 
> > > great minds think alike... here is the example I recently proposed 
> > > for addition in the spec:
> > > 
> > > https://pr-preview.s3.amazonaws.com/w3c/rdf-star/pull/225.html#marri

> > > ed-example
> > 
> > 
> > You use a new property :occurrence instead of :occurrenceOf in the 
> > example before that example. Is there a reason for that?
> > 
> > Also you use the abbreviated syntax. It might be helpful to use the 
> > un- abbreviated syntax in all examples except one section where the 
> > abbreviated syntax is explained. Your example does however show that 
> > the abbreviated syntax doesn't make anything better w.r.t. the 
> > wikidata usecase.
> > 
> > The way wikidata models this is arguably even more horrible. It is an 
> > ordered list with marriages of Richard Burton. Each marriage is a list 
> > entry which could be a blank node, etc. Elisabeth Taylor presumably 
> > has her own list of marriages and nothing but ardent querying connects 
> > the two lists I suppose.
> > 
> > 
> > > and that was before reading Ora's use-cases... ;)
> > 
> > The wikidata use case has been part of the RDF* use cases for a year 
> > now, or two?
> > 
> > 
> > Maybe it would be helpful to name this problem properly - not 
> > "wikidata usecase" but rather "multiset problem", or "multiset use case"?
> > 
> > 
> > Best,
> > Thomas
> > 
> > 
> > > > Wikidata's data model records their two marriages as edge 
> > > > annotations, on the
> > > > https://m.wikidata.org/wiki/Property:P26 relationship linking them.
> > > > 
> > > > Eg. https://m.wikidata.org/wiki/Q34851

> > > > https://m.wikidata.org/wiki/Q151973

> > > > 
> > > > From a Schema.org point of view, being able to express more of 
> > > > what Wikidata can do seems attractive for interop.
> > > > 
> > > > Dan
> > > > 
> > > > In Burton's entry we have :
> > > > spouse
> > > > 
> > > > Elizabeth Taylor
> > > > start time 15 March 1964
> > > > end time 26 June 1974
> > > > series ordinal 2
> > > > 1 reference
> > > > The Peerage person ID p33443.htm#i334430 retrieved 7 August 2020
> > > > 
> > > > Sybil Christopher
> > > > start time 5 February 1949
> > > > February 1949
> > > > end time 5 December 1963
> > > > series ordinal 1
> > > > 1 reference
> > > > The Peerage person ID p33443.htm#i334430 retrieved 7 August 2020
> > > > 
> > > > Suzy Miller
> > > > end time 1982
> > > > start time 21 August 1976
> > > > series ordinal 4
> > > > 0 references
> > > > 
> > > > Elizabeth Taylor
> > > > start time 10 October 1975
> > > > end time 29 July 1976
> > > > series ordinal 3
> > > > 0 references
> > > > 
> > > > Sally Burton
> > > > start time 3 July 1983
> > > > end time 5 August 1984
> > > > series ordinal 5
> > > > 0 references
> > > > 
> > > > 
> > > > On Thu, 2 Dec 2021, 21:12 Jos De Roo, <josderoo@gmail.com> wrote:
> > > > 
> > > >     Hi Ora,
> > > > 
> > > >     Very nice use cases and to me it looks quite natural to 
> > > > express
> > > >     them as
> > > > 
> > > >     :Bob :isMarriedTo :Alice .
> > > >     [] :repr << :Bob :isMarriedTo :Alice >>; :since 2020 ; :source
> > > >     :NYTimes .
> > > >     [] :repr << :Bob :isMarriedTo :Alice >>; :since 2021 ; :source
> > > >     :WashingtonPost .
> > > > 
> > > >     :M1 :pipe :M2 .
> > > >     [] :repr << :M1 :pipe :M2 >>; :size "DN 100"; :schedule "30" .
> > > >     [] :repr << :M1 :pipe :M2 >>; :size "DN 125"; :schedule "10" .
> > > > 
> > > > 
> > > >     Kind regards,
> > > >     Jos
> > > > 
> > > >     -- https://josd.github.io

> > > >     <https://josd.github.io>
> > > > 
> > > > 
> > > >     On Thu, Dec 2, 2021 at 7:44 PM Lassila, Ora <ora@amazon.com>
> > > > wrote:
> > > > 
> > > >         Folks,
> > > > 
> > > >         Attached is a document that outlines a couple of uses 
> > > > cases
> > > >         (variants of one modeling pattern ,really) we would like 
> > > > to
> > > >         submit for consideration by the upcoming RDF-star Working
> > > >         Group. I am submitting these now just in case this turns 
> > > > out
> > > >         to be relevant to how the charter gets written. Comments 
> > > > are
> > > >         welcome, and I am happy to discuss these use cases 
> > > > whenever.
> > > > 
> > > >         Regards,
> > > > 
> > > >         Ora
> > > > 
> > > >         --
> > > > 
> > > >         Dr. Ora Lassila
> > > > 
> > > >         Principal Graph Technologist, Amazon Neptune
> > > > 
> > > >         Amazon Web Services
> > > > 
> > > >         ora@amazon.com
> > > > 
> > 
> 
>

Received on Tuesday, 7 December 2021 01:21:52 UTC