Re: bNodes as local constants

Actually this is not a good example. A better way to approximate bnodes is
to translate them into skolem in the head and into existentials in the
body. This is how it is done in FLORA-2 and (I think I saw somewhere) cwm.

In your example _:x rdf:type Person to the right of "entails"
is a query, i.e., it is a body literal. So, it is translated into an
existential and everything is hunky-dori. (Existentials in rule bodies are
fine.)

This is not to say that this simulation is completely adequate, but this
particular case is not a problem.


	--michael  

> Dear all,
> 
> As fulfillment of my example to show that we cannot simply treat bNodes
> as local constants, here is a very simple example.
> 
> 
> In RDF we have
> 
> john rdf:type Person   entails   _:x rdf:type Person
> 
> where _:x is a bNode. The entailment relationship holds because there is
> an assignment for _:x which is the same as the   interpretation of the
> constant john.
> 
> 
> If we would translate _:x to a local constant, say, x, then this
> entailment relation no longer holds:
> 
> john rdf:type Person   not-entails   x rdf:type Person
> 
> Although john and x may denote the same individual in some
> interpretation, this is by no means the case in every interpretation
> which is a model of    john rdf:type Person.
> 
> 
> Best, Jos
> 
> -- 
> Jos de Bruijn,        http://www.debruijn.net/
> ----------------------------------------------
> When we remember we are all mad, the mysteries 
> disappear and life stands explained.
>   - Mark Twain
> 
> 
>

Received on Tuesday, 24 April 2007 21:42:20 UTC