Re: OWL2 monotonicity (was How do you deprecate URIs? )

On 16 Jul 2008, at 18:45, Booth, David (HP Software - Boston) wrote:

> Hi again Bijan,
[snip]
>> First, I don't think there is a monotonicity requirement. Certainly
>> not expressed from that section.
>>
>> Second, I don't see that this is nonmonotonic. OWL DL isn't an
>> extension of RDF or RDFS. This is well known. (It's an extension of a
>> subset of them.)
>
> To clarify my concerns:
>
>  - I think it is architecturally critical

BTW, just so we're on the same page, the phrase "architecturally  
critical" just tune me out. Please, give specific technical points  
instead.

(To see my 'tude:
	<http://clarkparsia.com/weblog/2008/01/15/tag-youre-not-it/>
	<http://clarkparsia.com/weblog/2008/06/30/architectural-arguments/>

Of course, you are free to do as you like. I'm just pointing out that  
these sorts of line don't work very well with me.)

> that for any RDF graph that may include non-OWL2 monotonic semantic  
> extensions,

!!!

> if the graph has entailments E without applying the OWL 2  
> semantics, then all of those entailments E should still be valid  
> when OWL 2 semantics are applied, i.e., the OWL 2 entailments  
> monotonically extend the existing entailments.

This isn't possible, I think. I mean, let's say you define the  
"class" owl:TransitiveProperty to be equal to owl:Nothing (this is a  
monotonic extension of RDF). P type owl:TransitiveProperty is now  
inconsistent under that monotonic extension (thus has all  
entailments) but not in OWL.

Various aspects of d entailment are another place ripe for such issues.

> (And yes, I mean "monotonic" in the usual sense.)

Not really. Monotonicity usually refers to what happens if you *add*  
axioms, not if you change the semantics.

>  - As described by Michael, OWL 2's annotation properties sound  
> like they would violate this, as you indicated they would for OWL 2  
> Full:
>
>> [ . . . ]
>>>> In OWL 2 Full, being an RDF compatible language, it is not
>>>> possible to
>>>> define such a kind of "semantic-freeness". Here, owl:sameAs
>>>> *will* transfer the deprecation triple to the other URI.
>
> I don't mean to irk anyone, but I do mean to be clear that I think  
> semantic monotonicity is architecturally *critical*, so that RDF tools

Tools can regardless, obivously.

> and reasoning can be safely applied to *all* RDF graphs, regardless  
> of whether or not a graph uses OWL 2.

It's unclear that this is really a problem in practice. Frankly,  
there are all sorts of minor strangenesses with the alignment between  
all theses languages.  I think it's a very bad idea to stick too much

>   This is particularly important when RDF graphs are combined from  
> many sources, some of which may use OWL 2 and others not.

Given the weakness of RDF semantics and the sort of entailments you  
may or may not have, I'm pretty skeptical that this is a serious  
problem.

IOW, architectural nicety needs to be weighed against lots of other  
consideration, including functionality.

> I hope this clarifies my concerns and the reasons for them.

Some, yes. But I don't think you've remotely made an all things  
considered case. For you, afaict, this sort of point is a trump card.  
It's not for lots of other people.

Cheers,
Bijan.

Received on Wednesday, 16 July 2008 18:16:49 UTC