Re: Where I am about floats, etc.

On Jul 7, 2008, at 8:18 AM, Ivan Herman wrote:

> Bijan Parsia wrote:
> [skip]
>> I think I'm specifically against including xsd:float and  
>> xsd:double as types at all at this stage, and even as our specing  
>> them out as optional. (We shouldn't forbid them; just be silent.)
> I know this is a side issue compared to the main thrust of the  
> discussion but I would still like to understand what 'non  
> including' and 'be silent' means in this case. What happens to  
> legacy data?
> My feeling is that being silent is not really possible. We should  
> specify what happens if a tool gets an ontology/data that is  
> perfectly o.k. in OWL2 DL or OWL2 EL++ but using, say, xsd:float  
> (or other, non included XSD datatypes, for that matter): should we  
> rule that the data is still o.k. in terms of, say, OWL2 EL++ with  
> an additional warning that the reasoning on datatypes might be  
> shaky, or would that data ruled to be incorrect and state it it OWL  
> Full? I think something has to be said in the specification somewhere.

It has been proposed that all the xsd:float literals is good "data".  
However, the data is interpreted, in the case of xsd:float, as of  
type owl:real in all cases other than +/-INF and NAN. Some further  
thought needs to devoted to this case. They do need to be  
roundtripped, in the use cases I anticipate. If the round tripping of  
OWL preserves the  float lexical representation, then from my point  
of view, this is satisfactory for the scientific data case I imagined.

The other cases where one might use xsd:float, is when it is used in  
a domain/range or restriction. Handling this is a bit more of an  
issue, however I would suggest that floats in this context be  
interpreted as owl:real, and similarly preserved in round tripping.  
Tools could warn about this, and offer to make the change.

In all these cases, I suggest we decide which choices we think should  
persist into future versions of OWL, and which are "experimental" and  
which future versions of OWL may wish to reexamine.

I'm been fairly convinced by Robs discussion as well the discussion  
and pointers discussion on the XML Schema list that schema datatypes  
are not conceived as the sort of thing that makes sense that  
languages like OWL. As a further point, I suggest we consider using  
language in our specification that differentiates itself from the  
language used to describe data types in XML Schema, in order to avoid  


> Personally, I would opt for the former, b.t.w., I suspect that  
> there are already a bunch of OWL1 DL data out there and we would  
> not want to refuse them from a DL point of view...
> Bijan, how does Pellet treat such cases? I guess you have met this  
> issue in practice...
> Cheers
> Ivan
> -- 
> Ivan Herman, W3C Semantic Web Activity Lead
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Received on Tuesday, 8 July 2008 16:03:35 UTC