Re: reifiesDomain-14 (Re: proposal: a reifier should reify only one "thing")

Sorry (switch ?start ?end to ?from ?to) in the previous post.
*Kurt Cagle*
Editor in Chief
The Cagle Report
kurt.cagle@gmail.com
443-837-8725 <http://voice.google.com/calls?a=nc,%2B14438378725>


On Fri, Apr 19, 2024 at 2:08 PM Kurt Cagle <kurt.cagle@gmail.com> wrote:

> Sasaki, Felix
> 1:11 PM (30 minutes ago)
> to me, ddooss@wp.pl, Pierre-Antoine, Ora, RDF-star
>
>> “The user usually doesn't see the predicate identifiers directly; they
>> only see the label“
>>
>> For creating data
>> CREATE        (liz:Person {name: 'Liz'}), (richard:Person {name:
>> 'Richard'})
>> CREATE        (liz)-[:MARRIED {from: 1964, to: 1975}]->(richard)
>> CREATE        (liz)-[:MARRIED {from: 1985}]->(richard)
>>
>> That does not bother them, and also not for querying the data
>> MATCH (liz:Person {name: 'Liz'})-[m:MARRIED]->(richard:Person {name:
>> 'Richard'})
>> RETURN m.from AS StartYear, m.to AS EndYear
>
>
> The issue is not that it bothers LPG viewers, but whether this can be
> rendered in RDF-Star. If you take this assumption naively (a direct
> translation) this becomes:
>
> << :m | :liz :marriedTo :richard >> :from 1964; :to 1975 .
> << :m | :liz :marriedTo :richard >> :from 1986 .
>
> This implies that you have the potential for:
>
> :m :from 1988; :to 1975 .
>
> which should be self-evidently wrong.
>
> Even though the MARRIED element looks like it's an identifier, it is STILL
> text, though probably text that is constrained. This is what I meant
> earlier about LPGs modelling the situation incorrectly. They can get away
> with it because the data is kept in the form of records, not assertions. In
> RDF, you don't have bundles of assertions (you do, but they are called
> named graphs, and I won't get into that discussion here).
>
> The statements above are still modelled as:
>
> <<:m1 | :liz :married-1 :richard>> :from: 1964, to: 1975 .
> <<:m2 | :liz :married-2 :richard>> from: 1985.
> :m1 rdfs:label "MARRIED".
> :m2 rdfs:label "MARRIED".
>
> Now this is not necessarily a deal breaker. You can readily query from
> this:
> SELECT ?bride ?groom ?from ?to WHERE {
> ?marriage rdfs:label "MARRIED".
> ?marriage rdf:subject ?bride .
> ?marriage rdf:object ?groom.
> ?marriage :from ?start .
> OPTIONAL {
>       ?marriage :to ?end
>        }
> }
>
> and this will give us the expected responses, but that's only because we
> have used the "MARRIED" label as an ersatz property URL, creating what
> appears to be a hypergraph relationship, if you assume that any hypergraph
> requires a proxy for a set (here rdfs:label is used as a subproperty of
> rdfs:member).
>
> That's why you have to be very careful about how close you create
> equivalencies between LPGs and RDF. LPGs hide a lot of the complexity, but
> they also don't handle multiplicities efficiently. RDF is more verbose, but
> is also more exacting in its specification.
>
> With regards,
>
> *Kurt Cagle*
> Editor in Chief
> The Cagle Report
> kurt.cagle@gmail.com
> 443-837-8725 <http://voice.google.com/calls?a=nc,%2B14438378725>
>
>
> On Fri, Apr 19, 2024 at 1:11 PM Sasaki, Felix <felix.sasaki@sap.com>
> wrote:
>
>> “The user usually doesn't see the predicate identifiers directly; they
>> only see the label“
>>
>>
>>
>> For creating data
>>
>> CREATE        (liz:Person {name: 'Liz'}), (richard:Person {name:
>> 'Richard'})
>>
>> CREATE        (liz)-[:MARRIED {from: 1964, to: 1975}]->(richard)
>>
>> CREATE        (liz)-[:MARRIED {from: 1985}]->(richard)
>>
>>
>>
>> That does not bother them, and also not for querying the data
>>
>> MATCH (liz:Person {name: 'Liz'})-[m:MARRIED]->(richard:Person {name:
>> 'Richard'})
>>
>> RETURN m.from AS StartYear, m.to AS EndYear
>>
>>
>>
>> Best,
>>
>>
>>
>> Felix
>>
>>
>>
>> *Von: *Kurt Cagle <kurt.cagle@gmail.com>
>> *Datum: *Freitag, 19. April 2024 um 21:53
>> *An: *ddooss@wp.pl <ddooss@wp.pl>
>> *Cc: *Pierre-Antoine Champin <pierre-antoine@w3.org>, Lassila, Ora <
>> ora@amazon.com>, RDF-star WG <public-rdf-star-wg@w3.org>
>> *Betreff: *Re: reifiesDomain-14 (Re: proposal: a reifier should reify
>> only one "thing")
>>
>> >> This is actually an error that arises in LPGs, because they have no
>> way of differentiating #marriage1 from #marriage3.
>>
>> > It's not true. Most PG definitions or implementations allow you to
>> create two edges with the same label and different properties.
>>
>>
>>
>> I'm saying that this is a modelling error with LPGs.  The edge contains
>> the identifier in the assertion, not the nodes. In an LPG (specifically
>> Neo4J):
>>
>>
>>
>> (Liz marries Richard) [from 1964; to 1975]
>>
>> and
>>
>>
>>
>> (Liz marries Richard) [from 1985]
>>
>> are distinct because the predicate "marries" carries the (implicit)
>> identifier, and any query is actually an query on the text of the labels.
>>
>>
>>
>> This is equivalent to
>>
>>
>>
>> <<:liz :marries-1 :richard>> [:from 1964 ; to: 1975] .
>>
>> <<:liz :marries-2 :robert>> [:from 1977 ; to: 1981] .
>>
>> <<:liz :marries-3 :richard>> [:from 1985] .
>>
>>
>>
>> :marries-1 rdfs:label "marries" .
>>
>> :marries-2 rdfs:label "marries" .
>>
>> :marries-3 rdfs:label "marries" .
>>
>>
>>
>> The user usually doesn't see the predicate identifiers directly; they
>> only see the label, so they don't recognize that the first and third
>> statements actually have different predicates with the same name. That is
>> CERTAINLY the case for Neo4J; I'm not sure about other LPGs.
>>
>>
>>
>>
>>
>>
>>
>> *Kurt Cagle*
>>
>> Editor in Chief
>>
>> The Cagle Report
>>
>> kurt.cagle@gmail.com
>>
>> 443-837-8725
>>
>>
>>
>>
>>
>> On Fri, Apr 19, 2024 at 12:30 PM ddooss@wp.pl <ddooss@wp.pl> wrote:
>>
>> Kurt Cagle <kurt.cagle@gmail.com>:
>>
>> <<#marriage1 | :liz :marries :richard>> a :Event;
>>
>>        :bride :liz ;
>>
>>        :groom :richard ;
>>
>>        :startYear 1964 ;
>>
>>        :endYear 1975 ;
>>
>>        .
>>
>>
>>
>> This works in the case where Liz later marries Bob:
>>
>>
>>
>> <<#marriage2 | :liz :marries :robert>> a :Event;
>>
>>        :bride :liz ;
>>
>>        :groom :robert ;
>>
>>        :startYear 1977 ;
>>
>>        :endYear 1981 ;
>>
>>        .
>>
>>
>>
>> But gets into trouble when Liz and Richard decide to remarry:
>>
>>
>>
>> <<#marriage3 | :liz :marries :richard>> a :Event;
>>
>>        :bride :liz ;
>>
>>        :groom :richard ;
>>
>>        :startYear 1985 ;
>>
>>        .
>>
>>
>>
>> This is actually an error that arises in LPGs, because they have no way
>> of differentiating #marriage1 from #marriage3.
>>
>>
>>
>> It's not true. Most PG definitions or implementations allow you to create
>> two edges with the same label and different properties.
>>
>>
>>
>> Best,
>>
>> Dominik
>>
>>
>>
>>