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#married-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 Friday, 3 December 2021 14:42:29 UTC