blank nodes are not transparent in the community group semantics

I was thinking about the various semantics for RDF-star and noticed something 
strange when equality (or any means to enforce equality) is considered.

In the community report I would have thought that

_:k owl:sameAs :j .
_:l owl:sameAs :j .
:c :d << _:k :y :z >> .
:a :b << _:l :y :z >> .

entails

:a :b << _:m :y :z >> .
:c :d << _:m :y :z >> .

because blank nodes are supposed to be transparent and so only their meaning 
counts.

But this is not the case because the first graph turns into (roughly)

_:k owl:sameAs :j .
_:l owl:sameAs :j .
:a :b _:kyz .
_:kyz unstar:subject _:k .
_:kyz unstar:predicate :y .
_:kyz unstar:object :z .
_:kyz unstar:predicateLexical ":y"^^xsd:string .
_:kyz unstar:objectLexical ":z"^^xsd:string .
:c :d _:lyz .
_:lyz unstar:subject _:l .
_:lyz unstar:predicate :y .
_:lyz unstar:object :z .
_:lyz unstar:predicateLexical ":y"^^xsd:string .
_:lyz unstar:objectLexical ":z"^^xsd:string .

and part of what the second graph turns into is

:a :b _:myz .
:c :d _:myz .

So the identity of _:k and _:l is important, not just their denotation.

peter

Received on Thursday, 4 May 2023 14:37:15 UTC