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RE: Locating things properly

From: Catherine Dolbear <Catherine.Dolbear@ordnancesurvey.co.uk>
Date: Thu, 12 Jun 2008 11:58:22 +0100
Message-ID: <62AD2163C9CF52469A380259227B79880366C55A@OSMAIL.ordsvy.gov.uk>
To: "Hugh Glaser" <hg@ecs.soton.ac.uk>, "Linking Open Data" <public-lod@w3.org>


Hi Hugh & LODers,

This seems to be about knowledge modelling and context. Your first
sentence is telling me a very general context/application - you want to
be able to map things. For that you need the lat/long [or you could buy
lots of lovely OS data and we'd give you a point for the exact building
address :-)].
 
WWW06 took_place_in Edinburgh, and Edinburgh is_located_at <lat/long
whatever> - for that you'd expect some central point of the whole of the
city of Edinburgh; but WWW06 took place at a different lat/long: so your
triples might be WWW06 has_address <address of conference centre>;
<address of conference centre> is_located_at <another lat/long>.
Depending on your context, you may need either one. E.g. if you're
travelling from the States to the conference, you probably only want to
see the lat/long for Edinburgh on your small-scale map, but if you're in
Edinburgh, trying to find the conference centre, you need the more
specific lat/long of WWW08's building.

It worries me a bit that we're simplifying stuff too much and losing
some of the semantics - these more detailed semantics allow you to
select the right data for your application. I don't think it's a
question of either/or.

Cheers,
Cathy 

-----Original Message-----
From: public-lod-request@w3.org [mailto:public-lod-request@w3.org] On
Behalf Of Hugh Glaser
Sent: 12 June 2008 10:05
To: Linking Open Data
Subject: Locating things properly


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
Way.
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://dbpedia.org/resource/Edinburgh>
 <http://www.w3.org/2003/01/geo/wgs84_pos#lat> ?lat .
<http://dbpedia.org/resource/Edinburgh>
<http://www.w3.org/2003/01/geo/wgs84_pos#long> ?long
}

Best
Hugh


--
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
http://www.ecs.soton.ac.uk/~hg/

"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
significance."


.


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Received on Thursday, 12 June 2008 10:59:13 UTC

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