Re: multisets everywhere

On Dec 21, 2021, at 03:23 PM, Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu> wrote:
> 
> In RDF semantics (both the current standard and the proposed RDF-star), a triple is either true or false. 


I believe this is the first time I've known anyone to suggest
that an RDF triple could be (semantically known to be) false.

How do you know whether a given triple is false?  Or, true?

My understanding has been that the original conception of RDF 
was that it would only be used to record universal and eternal 
facts; in other words, everything encoded in RDF was universal
and eternal truth.

(This was an immediate problem, because we all hopefully know 
that description accuracy requires that those descriptions be
changeable over time, but it was hard enough for many to grasp 
the simplicity of describing everything with SPO triples that 
it took years for many to realize that few descriptions were 
eternally accurate.)

On this basis, even though RDF officially and explicitly operates 
under the "Open World" assumption (where anything that is not 
stated is implied and should be inferred to be unknown), *some* 
unasserted values were in practice treated as if they had been 
asserted -- i.e., that once inscribed, a triple was now, had
always been, and would always be, accurate.

Operating on this universal and eternal truth assumption, all 
graphs in the universe could be combined, and there would be no 
contradictions, and all queries should deliver results that are 
likewise universally and eternally true.

This belief has been problematic since RDF began, and it is 
likely to continue to be so for many years if not forever.

In RDF 1.1, it was explicitly stated that any given graph must 
be treated as a snapshot of a universe, just a moment in time
(though still treated as if entirely true about that moment), 
and should only be blended (merged, unionized) with other graphs 
that described the same moment in time.

The only way to *know* whether any two Named Graphs were about 
the same moment in time is for those two Named Graphs to be 
explicitly described as such.  Often enough, even with this 
improvement, two observers who inscribed descriptions that 
were accurate from their perspective, included to few details 
about what made up their perspective for others to accurately
determine which graphs were from that same perspective, and
which were different.  (Just for discussion's sake, consider
two people, one to the north and one to the south of a fire,
describing that fire.  The wind was blowing west-to-east, so
smoke could accurately be described as drifting east -- but
the observers described it instead as drifting to the right
in one case and to the left in the other -- and both were
indeed accurate, but neither was *fully* accurate....)

All of which is to say, "This is far more complex than it
appears when we say 'S P O [G]' is all you need to describe
anything!"

Be seeing you,

Ted