From: Adam Pease (apease@ks.teknowledge.com)
Date: 03/10/03
Pete, At 12:56 PM 3/10/2003 -0500, Pete Haglich wrote: >The "locus" vs "location" was a throwaway ancedote about a particular >customer, I didn't mean for people to read too much into it. Ok, sorry if I read too much into this. >As far as the nature of a city being a point vs being a region, I think it >goes a bit deeper than what you suggest and it depends on the granularity >of the discourse. For example, for travel itineraries, cities are often >treated as points. Interesting. If I type a city into Yahoo and ask for directions, it chooses a default address within the city. When I get a travel itinerary, it's to a specific airport associated with a city. This still seems like an interface issue. The objective reality is that a city is a region. One may abstract it to a vague point in discourse or GUI, but that doesn't change the facts of what a city is. If one builds that abstraction into the ontology itself, that dramatically limits one's ability to reuse the ontology in a different content, or integrate with a GIS or other repositories of date, which are the purported benefits of using ontologies to begin with. Adam >However, there are other cases where the "two dimensional properties" of a >city are important. In our use of spatial ontology we have found it >useful to accomodate both viewpoints. I should note, though, that in our >use of DAML we don't have something like a "TerritoryFn" which might map >an idealized city point to the territory within the city limits. > >Pete > > >On Monday, Mar 10, 2003, at 12:42 US/Eastern, Adam Pease wrote: > >>Pete, >> That sounds like a lexicon issue, rather than an ontology issue. If a >> human user wants to use a particular term, that's an issue for the >> interface. A lot of problems occur when one tries to adjust an >> ontology, which must support inference, to conform to a human's >> linguistic conventions. We've found that it's straightforward to keep >> the two distinct, and have a lexicon file that maps to terms in an >> ontology. That also makes it easier to use the same ontology for users >> who speak different languages, as well as those who use different >> lingo. The issue of vagueness in language is related. A city is a >> region, which may have a centroid point that is represented on a map. A >> user may wish to be vague about that, but that's a language issue, not >> an ontology issue. >> >>Adam >> >>At 11:06 AM 3/10/2003 -0500, Pete Haglich wrote: >>>We have adopted that in our current spatial ontologies, using the term >>>"locus" because "location" had connotations to our customer. >>>The notion of "locus" has child subclasses of Point Locus, Linear Locus, >>>Area Locus, and Volume Locus. >>> >>>We find that the blurring of distinction between point and area is >>>sometimes useful when discussing things like cities. For some purposes >>>they are usefully modeled as points, in other cases, it is more >>>appropriate to reference the associated territory within the city limits. >>> >>> >>>On Friday, Mar 7, 2003, at 14:55 US/Eastern, Austin Tate wrote: >>> >>>>The idea being that a neutral word like location which does not restrict >>>>the meaning to be only one of a "point" or "area" or "volume" and leaves >>>>nature of the "location" open can be useful to allow relationships to be >>>>stated to give real meaning. >>>-- >>>Pete Haglich, ISX Corporation >>>Virginia Beach, VA >>>Mobile (757) 572-5913 >> >> >-- >Pete Haglich, ISX Corporation >Virginia Beach, VA >Mobile (757) 572-5913
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