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Re: Requirements for a possible "RDF 2.0"

From: Axel Polleres <axel.polleres@deri.org>
Date: Mon, 18 Jan 2010 11:43:57 +0000
Cc: <semantic-web@w3.org>
Message-Id: <620798AE-6356-4A0C-82BD-3D6E6FBB6AC6@deri.org>
To: Kjetil Kjernsmo <kjetil@kjernsmo.net>
Hi Kjetil,

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)

Axel


just my two cents
On 14 Jan 2010, at 21:43, Kjetil Kjernsmo wrote:

> All,
> 
> Like some others, I think the adoption problem is not solved by another
> spec, but by actually writing useful stuff. Still, I think there are things
> that should be fixed, but relatively minor things. I'm +1 on stuff like
> graph naming, kill bag, rec on serialisations, etc, but let me also bring
> forward one little thing that is of major importance: Units.
> 
> There are no good ways to express the units of numbers in RDF. Yet, most
> numbers out there are expressed with units. You could do it with datatype
> URIs, but datatypes are orthogonal to units. You could do it with some
> hacks, people have been doing that, but it quickly gets complicated and far
> from ideal. We really need a simple way to express units, and ways to make
> it possible for agents to convert numbers between different units.
> 
> Concrete example: Lets use DBPedia to find aircrafts with a certain maximum
> take-off-weight that can take off from airfields with a certain maximum
> runway length. All the data is on Wikipedia, and writing the SPARQL query
> should be easy (actually doing it is left as an exercise to the reader ;-)
> ).
> 
> But it can't be done, at least not without a lot of painful hacking on the
> client side, partly because not all the data is in DBPedia (notably, the
> take-off-run when the aircraft is fully loaded i.e. at MTOW), but
> importantly because of the units used, see e.g.:
> http://dbpedia.org/page/Stockholm-Arlanda_Airport
> where the numbers are dimensionless, and the unit is in the property, e.g.:
> dbpprop:r1LengthF, while the MTOW is expressed like this:
> dbpprop:maxTakeoffWeightMain    "20,200 lb"@en ;
> for http://dbpedia.org/page/Cessna_Citation_Excel
> 
> So, this is actually pretty useless. You cannot do the stuff that Linked
> Data should be good at with this.
> 
> So, you could say that this could be done Right and Consistently, whatever
> Right may be, but when we, as a community (DBPedia is our community
> project, right) has failed to do it Right, I would blame it on that it is
> too hard to do Right.
> 
> Not only is this important for everyday applications, it is also
> indispensable for most scientific applications. So, that's my main
> requirement.
> 
> Cheers,
> 
> Kjetil
> --
> Kjetil Kjernsmo
> kjetil@kjernsmo.net
> http://www.kjetil.kjernsmo.net/
> 
> 
Received on Monday, 18 January 2010 11:44:31 UTC

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