Re: question on rdfs:domain

On Feb 18, 2005, at 1:56 PM, abc def wrote:

>
> Is the following construct valid in owl:
>
> <owl:ObjectProperty rdf:ID="someProperty">
>     <rdfs:domain>
>       <owl:Class>
>         <owl:unionOf 
> rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#nil"/>
>       </owl:Class>
>     </rdfs:domain>
> </owl:ObjectProperty>
>
> The above construct is defining a property with an empty domain

No, it's defining a property with a domain that consists of the class 
rdf:nil (recently promoted from individual by  the power of OWL Full).

> which doesn't make much sense.

Sure it does. It's just the inverse of a property with the empty class 
(owl:Nothing).

>   What I am looking for is a place in the specifications (if any) that 
> says that such a construct is valid/invalid.

What sort of thing are you looking for? It's not OWL DL since the 
collection vocabulary is forbidden in the modeling domain. But it's 
perfectly ok, OWL Full. It really doesn't mean what you think it means, 
but what you thought it means is also definable (even in OWL DL).

Consider the following construct (in ad hoc syntax):
	an owl;Restriction onProperty someProperty
				    maxCardinality = 0

and this:

	an owl:Restriction onProperty theinverseof someProperty
				    maxCardinality = 0

and:
	an owl;Restriction onProperty someProperty
				    someValuesFrom owl:Nothing

and also:
	an owl:Restriction onProperty theinverseof someProperty
				    someValuesFrom owl:Nothing

(Hint, 1 and 3 say the same thing as do 2 and 4. If you make these a 
superclass of owl:Thing, then 2 and 4 are the same as a empty domain.)

Unless I've screwed it up due to fatigue :) But I don't think so 
glancing back.

I wouldn't focus on the spec per se (except to realize that owl:Nothing 
is the empty set), but on the logic of the constructs first. If you 
don't grasp that, the specs will not be helpful (since they, 
rightfully, presume a fair degree of logically fluancy).

Hope this helps.

Cheers,
Bijan Parsia.

Received on Saturday, 19 February 2005 05:47:18 UTC