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Re: motivation for bNodes/existentials in RDF; note for parsers

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Fri, 5 Apr 2002 13:50:00 -0600
Message-Id: <p05101506b8d3af7fefb4@[65.217.30.94]>
To: "Seth Russell" <seth@robustai.net>
Cc: <www-rdf-comments@w3.org>
>From: "Pat Hayes" <phayes@ai.uwf.edu>
>
>>  >Source A reads:
>>  >_:a  rdf:type :ball
>>  >_:a  :hasColor :blue.
>>  >_:a  :hasShape :round.
>>  >_:a  :ownedBy :Seth.
>>  >
>>  >Source B reads:
>>  ><uuid:1615>  rdf:type :ball.
>>  ><uuid:1615> :hasColor :blue.
>>  ><uuid:1615> :hasShape :round.
>>  ><uuid:1615> :ownedBy :Seth.
>>  >
>>  >Is this tantamount to the process A reading  "Seth owns some (maybe only
>>  >one) round blue balls."  and copying to B "Seth owns a round blue ball."?
>>
>>  No, the best way to render that output would be "Seth owns a round
>>  blue ball called '<uuid:1615>' ".
>
>Yes I get that.  But in the same vein what is your interpretation of the
>blank node above?   I was told that existential quantifiers meant:  'at
>least one exists such that'.   So (if bnodes are existential quantified
>variables) doesn't the blank node above mean the following?
>
>     "At least one round blue ball is owned by Seth."
>
>Now that certainly does not deny that:
>
>    "Seth owns a round ball called <uuid:1615>."
>
>But it doesn't make the same restraints on the world either . does it ?

We seem to be in violent agreement. The point is that knowing that a 
blue ball exists is not the same as knowing that it exists and is 
called by a certain name. So if you go from the former to the latter, 
then you are adding new information: you arent making a valid 
inference.

The other point is that from a purely logical point of view, making 
up a name is trivial and inconsequential, but I worry that from a 
web-sociological point of view it might be rather a more important 
kind of operation, to be treated with a bit more seriousness; more of 
a commitment, as it were.

Pat

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Received on Friday, 5 April 2002 14:49:59 GMT

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