Re: question on "forest-like anonymous individuals" restriction of OWL 2 DL

On 27 Jun 2009, at 17:11, Michael Schneider wrote:
[snip]
> But from what you say above, a second issue seems to arise: It looks  
> to me
> that OWL 2 DL now does not even allow to state /single/ property  
> assertions
> with blank nodes in both subject and predicate position. Because, as  
> you
> said, with
>
>  ObjectPropertyAssertion( ex:p _:s _:o )
>
> one will always also have
>
>  ObjectPropertyAssertion( InverseObjectProperty(ex:p) _:o _:s )
>
> and so there are in fact always /two/ triples

Triples aren't properties. There's only one property here. One  
relation. Think of the model.

> (though only one of them
> explicitly stated) with their contained blank nodes building a  
> circular
> structure.

To have a cycle you need at least two segments. Here you have a line  
which you can go back and forth on.


Consider
	_:x p _:y. _:y p _:z.

You *still* don't have a cycle. You can't get to x, through z without  
going through _:y *twice*. If it were a cycle, you could get back to  
_:x directly.

Cheers,
Bijan.