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Am 18.11.2014 um 18:06 schrieb Simon Spero:



> Suppose we have the following file:
> ---------------
> _:x rdf:type :Weasel.
> _:x :favoriteEggType :Chicken .
> ----------------
> 
> This says that there is something that is a Weasel and whose favorite type
> of egg is Chicken.
> 
> If we see this twice, we cannot tell how many chicken pickin Weasels we
> have.

I found that statement of yours a bit ambiguous and hope you don't mind
me trying to clarify:

It depends on /where/ we see this...

In the file you mentioned there is /one/ anonymous chicken pickin weasel
temporarily referred to as (named) _:x

Any repetition of the statement and any other statement using _:x in
subject or object position would refer to the very same weasel, *as
long as stated in the same file*.

(It's exactly as in your usage of "the following file": You don't
give it a name and if you use the same words in another mail I
couldn't know whether it is the one from this mail or a completely
new one...)


> A different file could use _:x to refer to some Chicken.

There the differences start as we can never tell whether _:x in
the different file is the same one or a different one anonymous
animal.

In practice this matters when one wants to add or remove individual
statements or subgraphs from graphs: When the graphs or subgraphs
have blank nodes as their origin, you usually can't.

viele Gruesse
Thomas Berger


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