Re: Against the notion of reification well-formed graph (i.e., atomicity)

On 23/01/2024 12:08, Thomas Lörtsch wrote:
> 
> 
>> On 23. Jan 2024, at 12:50, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
>>
>> On 1/23/24 06:30, Thomas Lörtsch wrote:
>>>> On 23. Jan 2024, at 12:22, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
>>>>
>> [..]
>>>>
>>>> What the proposal does talk about is RDF reifications, nodes in an RDF graph that are subjects of rdf:subject, rdf:predicate, or rdf:object triples.  The well-formedness requirement states that an RDF graph is ill-formed if it has a node that is the subject of a triple with any of these predicates and is not the subject of exactly
>>> Shouldn’t this be changed to *at least*? See my prior mail in response to Dörthe.
>>>> one triple with each of these predicates.  No bijection between triples and anything is either mentioned or implied.  The notion of well-formedness is completely syntactic.
>>
>> [...]
>>
>> The proposal is *exactly*.  Changing to *at least* could make it harder to optimize RDF reifications in implementations.
>>
>> As far as I can tell, multiple subjects, predicates, or objects is more difficult to optimize than missing subjects, predicates, or objects, but I haven't implemented an RDF triple store that optimizes RDF reifications.

Are there any today that make specific optimization for reification?

> But what does it *mean*? Optimizations should only be applied after we know that it means what we want it to mean.

Agreed.

We can start with our goals. "bloat" has been used in two senses : 
"visual bloat" and "size bloat".

Is the WG addressing the size bloat issue?

Optimization is not just storage space (and the choices there change 
over the space of a few years at the moment) - it's also preserving the 
outcome of queries.

What does SELECT (count(*) AS ?C) { ?s ?p ?o } return?
or any query with a ?p.

     Andy

> 
> I just realized that saying *at least* makes an implicit assumption about different terms in object position refering to the same entity in the realm of interpretation, i.e. a kind of owl:sameAs-ness. That may be way beyond what we want fix, and insofar saying *exactly* might be the safer and more restrained definition.
> Still it introduces a hint of opacity that I’m not happy with.
> 
> Thomas
> 
>> peter
>>
> 
>

Received on Thursday, 25 January 2024 11:08:57 UTC