Re: Requirements for a possible "RDF 2.0"

On Mon, Jan 18, 2010 at 4:59 PM, Pat Hayes <phayes@ihmc.us> wrote:
>
> On Jan 18, 2010, at 10:28 AM, Kjetil Kjernsmo wrote:
>
>> On Monday 18. January 2010 12:43:57 Axel Polleres wrote:
>>>
>>> As for units: Is there any reason why rdf:value could not solve your
>>> problem? (Although I admit that it might not be as widely used and it
>>> would be good to give it more weight, or resp. refine and push best
>>> practices in this direction more)
>>
>> Mainly that it has its complexity in the wrong places :-) (OK, I admit, I
>> had forgotten about it, I have never seen anyone use it. Pragmatically,
>> when something has so many use cases, yet seen very little use, it is
>> often
>> because its design is flawed).
>>
>> The unit is a property of the literal, not a property of the resource. By
>> requiring another node, it makes it harder to query, harder to write,
>> harder to read and harder to understand.

Agreed.

>
> But how else would you naturally express a property of anything in RDF, than
> by writing a triple? It sounds like you want to not be using RDF at all :-)

>
>>
>> Also, how would you formulate a conversion between units (e.g. lb to kg)?
>> Or use derived units (e.g. watt = joule / second)? That's complexity we
>> should tackle, not additional triples.
>

Well, that would probably require arithmetic, which is outside of RDF
and OWL (unless OWL2 has added something I don't know about quite
yet!)

> In another life, I am, with many others, working on an ontology for measures
> and units, which will among other things define a large number of
> conversions and unit/dimension derivations. It is quite complicated to state
> these, and certainly well beyond the expressive capabilities of RDF or even
> OWL. I don't think that this should even be contemplated as an RDF built-in
> feature.

But how about:

a b "blah blah z"

as in ex:London ex:hasTemp "10 ex:Celsius"

where z is a URI for a custom data-type that defines a relationship to
the base XML Schema data-types?

RDF needs to take syntactic sugar seriously. So, we could imagine that
then we could decompose

a b "blah blah z" -> a b "blah blah" AND "blah blah" rdf:value z"

i.e.

ex:London ex:hasTemp "10" AND "10 rdf:value ex:Celsius"

Although we should of course have restrictions on data merging
subjects as literals.

>
> Pat Hayes
>
>
>>
>> Cheers,
>>
>> Kjetil
>> --
>> Kjetil Kjernsmo
>> kjetil@kjernsmo.net
>> http://www.kjetil.kjernsmo.net/
>>
>>
>
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Received on Monday, 18 January 2010 17:08:18 UTC