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Re: Requirements for a possible "RDF 2.0"

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 18 Jan 2010 11:00:39 -0600
Cc: Kjetil Kjernsmo <kjetil@kjernsmo.net>, semantic-web@w3.org
Message-Id: <FD78D80A-8BA0-48D7-BCC2-442D29639882@ihmc.us>
To: Harry Halpin <hhalpin@ibiblio.org>

On Jan 18, 2010, at 8:18 AM, Harry Halpin wrote:

> Re adoption, basically I can't really point most hackers or
> implementers at the RDF specs without terrifying them (yes, syntax
> matters). A lot of them get overwhelmed - so when explaining RDF for
> the first time, to be honest I tend to point them at TimBL's N3
> tutorial [1] and *then* the specs.
> A simplification of the current specs is needed, with the things
> everyone uses (i.e. named graphs) added into the spec, with things
> like bags and list dropped. I also would like to have a decent way to
> express ordered lists in RDF and a clearly blessed (i.e. Turtle)
> syntax, along with JSON and Atom serializations. I think this is
> important for the future of RDF - new apps are great, but we need more
> programmers, and giving the specs a spring-cleaning would help.

Well, you need tutorials/ introductions/ RDF-for-Dummies stuff. That  
is being written, but it s not what should be in a spec, right?


> On Thu, Jan 14, 2010 at 9:43 PM, Kjetil Kjernsmo  
> <kjetil@kjernsmo.net> 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.
> +1. This is a major problem - one that also haunts XML Schema
> Data-types. Jen Tennison has some excellent work in this area [1].
> Perhaps extensible data-typing is what is needed?
> [1] http://www.w3.org/2000/10/swap/Primer.html
> [2] http://www.jenitennison.com/datatypes/
>> 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/

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Received on Monday, 18 January 2010 17:01:42 UTC

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