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Re: Requirements for a possible "RDF 2.0"

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Mon, 18 Jan 2010 14:18:22 +0000
Message-ID: <b3be92a01001180618m71c8cc20x150c6ef46b329a26@mail.gmail.com>
To: Kjetil Kjernsmo <kjetil@kjernsmo.net>
Cc: semantic-web@w3.org
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.

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/
>
>
Received on Monday, 18 January 2010 14:18:57 UTC

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