Re: Datatype normalization

Unfortunately correct :-) It might be worth pointing out that even plain literals in RDF effectively have a type already: they are character strings. So being 'untyped' should not be read as 'not yet having a type assigned' but more like 'known to have the type of a simple character string'. It is just like being typed with xsd:string, in fact. Thus, the example given by Nathan is already a type clash, and could give rise to an error (inconsistency) message from a type-savvy reasoner, since "12.2" is definitely not an xsd:decimal. 

Pat

On Nov 12, 2010, at 6:59 AM, Graham Klyne wrote:

> Nathan wrote:
>> Hi All,
>> I'd suggest that a high percentage of the worlds RDF data is being published untyped, where plain literals are used as rather than typed literals "12.2" vs "12.2"^^xsd:decimal, and also (to a lesser extent) "strings as"^^xsd:string's.
>> Until today, I had assumed that it was pretty "safe" to, upon parsing, turn xsd:strings in to plain literals / pull the datatype from the range of a property and turn the object in to the correct type.
>> However, it's been suggested to me today that this probably isn't a good thing / "the right thing" to do.
>> And thus, should I be avoiding implementing this feature, and additionally what are the reasons *not* to do this.
>> An example:
>> Ontology contains..
>>   ex:prop rdfs:range xsd:decimal .
>> "data" contains..
>>   :foo ex:prop "12.2" .
>> What reason would there be not to just infer/pull the type and convert to a typed literal?
> 
> Logical monotonicity.  That is, adding new facts to an RDFgraph should not invalidate inferences already made.
> 
> Attractive as it is, the mechanism you propose for inferring datatypes from rdfs:range declarations falls foul of this, as inferences you might make in the absence of rdfs:range statements may become incorrect when they are added to the graph.
> 
> I see this is part of the price we must pay for supporting an open-world, "missing-isn't-broken" [1] system for data on the web.
> 
> #g
> --
> 
> [1] this phrase due to Dan Brickley - http://rdfweb.org/mt/foaflog/archives/2003/07/24/12.22.48/ - unfortunately that URI has gone 404 (Dan: is this uncoolness permanent or transient?)
> 
> 
> 
> 

------------------------------------------------------------
IHMC                                     (850)434 8903 or (650)494 3973   
40 South Alcaniz St.           (850)202 4416   office
Pensacola                            (850)202 4440   fax
FL 32502                              (850)291 0667   mobile
phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes

Received on Monday, 15 November 2010 14:59:29 UTC