# Re: Blank nodes semantics - existential variables?

From: Thomas Passin <tpassin@tompassin.net>
Date: Mon, 29 Jun 2020 17:35:39 -0400

Message-ID: <614faf6b-f3b6-8e01-e244-12458902a70a@tompassin.net>
On 6/29/2020 4:17 PM, thomas lörtsch wrote:
> I used a rethoric figure, I think it’s called reductio ad absurdum. I want to say that assuming all different existentials may point to one and the same thing leads to rather non sensical interpretations like the one you just gave. Which is why I think it’s very unintuitive.

identification of nodes, whether bnodes or not.  There are basically two
ways to identify a "thing":  by its intrinsic identifier (its URI for
rdf graphs) or by its properties.  In fact, I don't see why a node's URI
identifier couldn't be considered just another property.

Identifying a node by its collection of properties may give a unique
identity or it may not, depending on those properties.  Since any given
collection of properties must be finite - we can't write down an
infinitely large rdf graph - and since presumably there could be an
indefinitely large number of unique nodes, it may be that most bnodes in
a specific graph will not be unique under an open world assumption.  But
that does not imply that any specific bnode is or is not unique.

In view of the above, there is no point in thinking about a default case
for the distinctness of different bnodes.  This would have to be
established in each case for the actual bnodes by their actual properties.

> what are the chances that I just repetaed my self versus that I want
to express that there are two different things that Bob has and that are
worth mentioning?

How can we know what those chances are, even if we were willing to use
probability to establish logical conclusions?  Suppose, for example,
that a witness to a store robbery reports seeing a large man breaking
the store's window at 11 AM, and another witness reports seeing an
average size man running out the store's door at 11:05.  Each of them
has seen a man, but were they both the same man?  It is impossible to