- From: Catherine Dolbear <Catherine.Dolbear@ordnancesurvey.co.uk>
- Date: Thu, 12 Jun 2008 11:58:22 +0100
- 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." . This email is only intended for the person to whom it is addressed and may contain confidential information. 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Received on Thursday, 12 June 2008 10:59:13 UTC