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Locating things properly

From: Hugh Glaser <hg@ecs.soton.ac.uk>
Date: Thu, 12 Jun 2008 10:05:07 +0100
To: Linking Open Data <public-lod@w3.org>
Message-ID: <C476A553.25162%hg@ecs.soton.ac.uk>

Hi LODers,

There seems to be quite a bit of stuff about being able to map things, and
so we need to know lat&long for the stuff we are considering.

But, saying where things are by adding lat&long is not the True Linked Data
Well, in general.
The right way is to say where things are by saying where they are.

For example, we should say that WWW2006 was in <Edinburgh, UK>, or
preferably something like <http://dbpedia.org/resource/Edinburgh>

Why not just put lat&long?
Well, for a start, the next question someone will ask is "Tell me all the
conferences that had Semantic Web stuff that happened in Scotland?" (oh
dear, someone just did that for people). Not fun to do with only lat&long.
(It would be wrong to say that we should keep both <Edinburgh, UK> and
lat&long; if someone has gone to the trouble of maintaining the lat&long for
<Edinburgh, UK>, why should I copy it somewhere else?)

Also, what format did you want it in? Are you going to give it to me as
WGS84, OS, UN Locode? Or do I need to invoke a service to get from one to
the other? And do I want (xsd:float) or (xsd:double)? dbpedia will give me
both geo:long and p:longitude, for example.

And if you are asking for input, I think it is fair to say that I am  more
likely to type (Edinburgh, UK) correctly (or better still, see it
auto-complete), than type in (55.95000076293945, -3.180000066757202) without
error and in the right order.

Which brings us to another issue: actually lat&long is too specific while
not being easily accurate enough. The conference was unlikely to be at the
lat&long that I specify, unless I get google maps or something to find out
the values for the place it was at. And it was not just at one place - it
used a number of rooms at slightly different places. Saying it was in
<Edinburgh, UK> is representing the knowledge right.

So if you want to construct an input form for me to say where something is,
please do something that lets me use towns and countries, preferably in a
way that links to something like dbpedia.

If we can't set up our systems and applications to use the Linked Data
Planet to get from <http://dbpedia.org/resource/Edinburgh> to the lat&long
in a format and accuracy we want, then I don't see how we can expect anyone
else to use it.

And how can you actually find out where Edinburgh is?
Just resolve <http://dbpedia.org/resource/Edinburgh> and process the RDF, or
Sparql it at http://dbpedia.org/sparql with

SELECT ?lat ?long WHERE {
 <http://www.w3.org/2003/01/geo/wgs84_pos#lat> ?lat .
<http://www.w3.org/2003/01/geo/wgs84_pos#long> ?long


Hugh Glaser,  Reader
              Dependable Systems & Software Engineering
              School of Electronics and Computer Science,
              University of Southampton,
              Southampton SO17 1BJ
Work: +44 (0)23 8059 3670, Fax: +44 (0)23 8059 3045
Mobile: +44 (0)78 9422 3822, Home: +44 (0)23 8061 5652

"If we have a correct theory but merely prate about it, pigeonhole it, and
do not put it into practice, then the theory, however good, is of no
Received on Thursday, 12 June 2008 09:05:54 UTC

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