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Re: how to define that a relation is a dataype?

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 22 Feb 2010 14:17:31 -0600
Cc: Story Henry <henry.story@bblfish.net>, Semantic Web <semantic-web@w3.org>, Dan Connolly <connolly@w3.org>, foaf-protocols@lists.foaf-project.org
Message-Id: <6D9D9DD4-44B4-4FC8-980E-F5EAF0C01856@ihmc.us>
To: Jeremy Carroll <jeremy@topquadrant.com>

On Feb 22, 2010, at 12:19 PM, Jeremy Carroll wrote:

> Pat Hayes wrote:
>>
>>>
>>> If xsd:integer is the set of all numbers, then how can it also be  
>>> a map from numbers to strings?
>>
>> In RDFS, the same name can be used to mean a mapping and a class  
>> and an individual. Same is true in OWL 2 and ISO Common Logic.  
>> Saves a lot of name-inventing. We used this in the datatyping. Used  
>> as an individual, the dtype name means the actual datatype as a  
>> thing, so we can say that "it" is a datatype for example. Used as a  
>> class name, its the class of all the values. Used as a property, it  
>> is the string-to-value mapping.
>>
>>
>
> It seems that, at least for Henry's own datatypes, he can also  
> decide to use the same name as a property. To give it the semantic  
> force he wants, he needs to use a semantic extension (as defined in  
> RDF Semantics), but I don't think there is too much to do to make  
> his desired triples true:
>
> 1234 :base64 "TU";
>    :hex "4D2";
>    :dec "1234";
>    :oct "2322";
>    :bin "11010010" .
>

Agreed, no problem there. But if he wants those to be RDFS datatypes  
as well, then he does have a problem.

>
> or
>
> _:b1234 owl:sameAs "1234"^^xsd:int .
>
> _:b1234 :base64 "TU";
>    :hex "4D2";
>    :dec "1234";
>    :oct "2322";
>    :bin "11010010" .
>
> and if he also declares these as RDF datatypes, and his RDF  
> processor is aware of both:
> - his semantic extensions defining the properties
> - and his new custom datatypes
>
> then
>
> all the following is true as well:
>
>
>
> _:b1234 owl:sameAs "1234"^^xsd:int .
>

OK, but not these:

> _:b1234 owl:sameAs "TU"^^:base64;
>    owl:sameAs "4D2"^^:hex ;
>    owl:sameAs "1234"^^:dec ;
>    owl:sameAs "2322"^^:oct ;
>    owl:sameAs "11010010"^^:bin .

If :hex is a map from numbers to strings, it definitely is not an RDFS  
(or indeed an XML) datatype. I really think this is more than just  
being nice: this would not be a semantic extension, as it violates a  
normative part of the existing specification.

Pat

>
> DanC said:
> [[ That's completely arbitrary; ]]
>
> But the whole point of a standard is to make those arbitrary  
> decisions consistently for everyone to aid interoperability!
> I think if Henry chooses to use the extension points, he can achieve  
> his goals; but then he loses the interop that is everyone's goal  
> (because other people won't know his extensions)
>
> I didn't much favor the datatyping framework we came up with, and I  
> prefer Henry's approach - but it's water under the bridge. I have a  
> strong preference that we all do it the same way. So I would urge  
> Henry against doing it different just to be different, and suggest  
> he should consider my second set of examples, where he is using his  
> own custom datatypes, but in the same datatyping framework as  
> everyone else, rather than reinventing the datatyping framework as  
> well. Real people don't type triples ... so there is going to be  
> some transform somewhere, and transforming to the second batch is no  
> harder than the first.
>
> Jeremy
>
>
>

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Received on Monday, 22 February 2010 20:18:02 GMT

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