Re: OWL-Time - issue with SPARQL endpoints lacking owl reasoner

Simon,

It really remains true that RDF and OWL do a lousy job with numeric values, from different value spaces to precision to units. There should be bigger answers to to these questions. However, there isn’t any present resolution within OWL 2. The only way a literal comparison can be made is if two datatypes derive from the same primitive datatype so a logical re-casting can be made. The types xsd:decimal, xsd:float, and xsd:double are deliberately set as pairwise disjoint to prevent such a comparison. We’re down and being kicked too. So the union may combine the value spaces of the types, but it doesn’t provide any means of overcoming the disjointness. It would only work if, as with coordinate string literals, the type you defined were intercepted and re-cast by a particular software engine. Maybe we need “NumSPARQL”.

—Josh

> On Apr 12, 2017, at 4:28 AM, simon.cox@csiro.au wrote:
> 
> [Now logged as ISSUE-178 - https://www.w3.org/2015/spatial/track/issues/178 ]
> 
> Very helpful Antoine. 
> 
> 1) clarifies what can be expected from a SPARQL engine (no OWL entailments, unless you specifically enable them!) 
> 
> 2) I knew about the XSD story, but not that OWL union datatypes were as pointless as you appear to be saying. So looks like TBC is cheating somehow. Its doing a good job though - I've tweaked my dataset to mix xsd:double, xsd:decimal, xsd:float and time:Number and am getting a sensible result. Definitely *not* just a lexical op. 
> 
> 3) but regarding your recommendation, I had more or less reached that conclusion already myself. xsd:decimal really is the only type to use - it gives arbitrary precision and magnitude, just sometimes a little inconvenient when working with the text representation. But since literal types are essentially about the serialized/lexical form, there are really no shortcuts. (You can probably express this more correctly.) (And I won't include the commas in the long numbers. BTW ISO standards officially recognize the French notation - comma for decimal, period for groups of three in big numbers, but I don't know if any computer languages do? ) 
> 
> This afternoon I already changed all except time:numericPosition and time:numericDuration to xsd:decimal (even before your mail landed). I guess I should finish the job. 
> 
> Simon 
> 
> -----Original Message-----
> From: Antoine Zimmermann [mailto:antoine.zimmermann@emse.fr] 
> Sent: Wednesday, 12 April, 2017 17:33
> To: Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au>; public-sdw-wg@w3.org
> Cc: dfils@oceanleadership.org
> Subject: Re: OWL-Time - issue with SPARQL endpoints lacking owl reasoner
> 
> Simon,
> 
> 
> I have several remarks wrt to your message concerning:
>  1) SPARQL engines supporting OWL
>  2) numeric values in XSD, RDF and OWL
>  3) precision & scientific notations (also related to your following email)
> 
> ... etc ...

Received on Wednesday, 12 April 2017 13:21:38 UTC