On Jun 16, 2008, at 4:21 AM, Story Henry wrote:

> On 15 Jun 2008, at 22:31, Alan Ruttenberg wrote:
>> I didn't suggest removing it. I suggested modularizing the  
>> ontology so that the portion is OWL DL can easily be used without  
>> having to hack anything. I suggested doing that in a way that the  
>> OWL Full version remained the same, without making it more  
>> difficult to keep two versions in sync, by using owl:imports to  
>> have the   Full version include the portion that is OWL DL.
>> In other situations, I have made suggestions, on the FOAF side of  
>> things, for how to improve it, and on the OWL side of things on  
>> how to make it possible for OWL2 to work with FOAF as is (or with  
>> minor changes)
>> What makes you think I want to harm FOAF?
> I don't see Tim suggesting you wanted to harm foaf anywhere in what  
> he wrote.

Here is what I read as such:

>> there is no reason to remove this valuable (essential) information  
>> from the ontology

I took this as saying suggested removing essential information from  
the ontology (a harm). If I've misinterpreted that, please excuse me.

To be clear,  I made no such suggestion. What I did suggest was that  
there are more than one community of users on the Semantic Web, and  
that there was a solution that could work for all. The suggestion you  
and Tim make does not work for one of those communities.

Speaking for that community: first, we don't write our own reasoners,  
we use ones that other people write. Second we depend on those  
reasoners to check our work. That checking happens in two ways. We  
depend on the reasoner to check that what we say is consistent, and  
once so depend on it getting *all* entailments. In order that we can  
reasonably expect that  it to do this reasoning, we check that we are  
giving it what it can handle, by running a "species validation" - a  
check that the ontology only says things that a DL reasoner knows  
what to do with. It is very common that errors are exposed at both  
stages - that is: both case where an ontology turns out to be  
detected to be not OWL-DL as well as cases where an ontology is found  
to be inconsistent. In the majority of such cases I have examined,  
these turn out to be actual errors.

I hope you don't expect that we would sacrifice this extremely useful  
functionality, or to hack our reasoners to say:  FOAF, as of this  
date, uses OWL Full correctly without modeling error, so please don't  
warn about that. Or to examine the noncompliance warnings in every  
case and verify that they only contain ones related to FOAF?

So, let me reiterate: My proposal was to create a win/win situation.  
FOAF doesn't change what expressivity it uses, but as a courtesy to  
OWL-DL users, factors the ontology so that the OWL-DL portion is in  
one file and that the full version imports that file and adds the  
remaining axioms that do not fall under OWL-DL. I'm happy to do this  
editing work if that would help.

Let me also reiterate that it is my sincere hope that OWL 2 will be  
able to support the full expressivity that FOAF uses. This is  
something that is on my mind, and which I actively advance within the  
working group.



> He is just suggesting that your reasoner do the selection between  
> owl-full and owl-dl itself. That is how I do things with the  
> Semantic Address Book at
> I don't even use owl-light, but some subset of that that I feel  
> comfortable with. The rules I use currently are here:
> (I explain in more details here
> opening_sesame_with_networked_graphs
> how I use this)
> I will be adding more rules and so use more of owl as I go along.
> Do as much reasoning as you have time for and as your inference  
> engine is capable of. That is what we humans do all the time.

> Henry
>> -Alan
>> On Jun 15, 2008, at 3:09 PM, Tim Berners-Lee <> wrote:
>>> Alan Ruttenberg wrote:
>>>> It's OWL, but not OWL-DL.
>>>> I would very much like there to be an OWL-DL version too, or at  
>>>> least to factor it into two components - an OWL-DL portion, and  
>>>> a set of further axioms that are imported by OWL full users.
>>> Why don't you hack your  OWL DL reasoner so it just ignores the  
>>> fact that something is an InverseFunctionProperty when it is also  
>>> a DatatypeProperty?  Just because the reasoner can't handle it,  
>>> there is no reason to remove this valuable (essential)  
>>> information from the ontology.
>>> Tim

Received on Monday, 16 June 2008 16:11:28 UTC