Re: RDF-star vs Wikidata for modelling Richard Burton

On 09/12/2021 13:50, Andy Seaborne wrote:
>
>
> On 09/12/2021 11:32, Pierre-Antoine Champin wrote:
>>
>> On 09/12/2021 12:23, Andy Seaborne wrote:
>>>
>>>
>>> On 08/12/2021 08:07, Pierre-Antoine Champin wrote:
>>>>
>>>> On 07/12/2021 22:25, Peter Patel-Schneider wrote:
>>>>> On Tue, 2021-12-07 at 14:52 +0100, Pierre-Antoine Champin wrote:
>>>>>> In LPGs as well, there is a point were modelling marriages or pipes
>>>>>> as edges will hit a wall. More specifically, if you want to relate
>>>>>> them to other *nodes* of the graph (link a marriage to its location,
>>>>>> link a pipe to its manufacturer), you also need to reifiy them as
>>>>>> nodes.
>>>>> I see some formulations of property graphs where edges can only be
>>>>> related to values, but is that really the case for all property 
>>>>> graphs?
>>>>
>>>> I have never seen an explicit definition of "Property Graphs" where 
>>>> this was not the case (but I have not seen them all, of course).
>>>>
>>>> I also have the feeling that allowing nodes as property values 
>>>> would pervert the idea of PGs, where the distinction between the 
>>>> internal structure of nodes (properties) and relation with other 
>>>> nodes (edges) is considered an important feature.
>>>
>>>
>>> Looking at some of the JSON serializations at property graphs - they 
>>> don't allow for edges to be nodes.
>>>
>>> There are two styles:
>>>
>>> * Nodes have integer ids, and edges are represented by start-end id 
>>> pairs and a label.
>>>
>>> * Edges have ids but the numbering of nodes and edges starts 
>>> separately at 0 so there are different numbering spaces.
>>>
>>> Both cases mean only attributes on edges.
>>
>> The way I read Peter's question was : are there PG implementation in 
>> which properties (I assume that's what you mean by "attributes") have 
>> nodes as their value?
>
> >>>> where edges can only be related to values
>
> I haven't found any serializations that put nodes or edge ids in the 
> data model.
>
> The serializations have values that are strings and numbers 
> (JSON-centric). Nothing else.
>
> Which formalizations have a type system for values?

Ian Hidders and Juan Sequeda presented the model used by the PG Schemas 
working group, during the SCG workshop [1] (slides and video are 
available). IIRC, they envision structured types for property values. 
But I don't think Nodes and Edges can be the value of properties.

[1] https://mosaicrown.github.io/scg2021/#mu-schedule



>
>     Andy
>
>>
>>>
>>>     Andy
>>>
>>>>
>>>>> (Well, if you think of Wikibase as a property graph formulation then
>>>>> there is at least one counterexample.)
>>>>
>>>> It never occurred to me to put Wikibase in the "Property Graph" 
>>>> family. I see some similarities, but also many differences. In 
>>>> particular, the distinction I mentioned above (between "properties" 
>>>> and "edges" of a node, in PG parlance) does not exist in Wikibase, 
>>>> where there all represented as "statements" (except for labels and 
>>>> descriptions... but I hope you see my point).
>>>>
>>>>    pa
>>>>
>>>>>
>>>>> peter
>>>>>
>>>>>
>>>
>