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Re: properties as nodes etc.

From: Wolfgang Nejdl <nejdl@kbs.uni-hannover.de>
Date: Tue, 25 Jun 2002 22:52:03 +0200
Message-Id: <200206252052.WAA28755@vivaldi.kbs.uni-hannover.de>
To: Graham Klyne <GK@ninebynine.org>
cc: Danny Ayers <danny666@virgilio.it>, pat hayes <phayes@ai.uwf.edu>, www-rdf-logic@w3.org

> 
> At 07:28 PM 6/25/02 +0200, Danny Ayers wrote:
> 
> 
> > >WHY is this perceived as a problem? What use is there in referring
> > >to edges?
> >
> >hmm...
> >
> >[the cat] --[sat on]--> [the mat]
> >                 |
> >               [for]
> >                 |
> >                 V
> >             [an hour]
> >
> >could currently be broken down something like :
> >
> >[sat on] --[subclass]--> [sat on for an hour]
> >
> >[the cat] --[sat on for an hour]--> [the mat]
> >
> >[sat on for an hour] --[cardinality]--> [1]
> >
> >but it seems less clunky to say :
> >
> >[sat on for an hour] --[instanceOf]--> [sat on]
> >
> >[the cat] --[sat on for an hour]--> [the mat]
> 
> Then if I say:
> 
>    [the dog] --[sat on for an hour]--> [the cat]
> 
> this is clearly another instance of [sat on for an hour].  I.e. we're back 
> to where we started.
> 

No. You would have

[the dog] --[sat on]--> [the cat]
                 |
               [for]
                 |
                 V
             [an hour]

Referencing an arc (actually, a triple) by a specific ID, by the way,
is useful exactly in these cases, where relationships have additional
attributes. Another example would be

[John] -- [married] -- [Mary]
               |
        [date of marriage]
               |
               V
         [July 4th, 1999]

or 

[table] -- [connected to] -- [leg]
               |
        [kind of connection]
               |
               V
             [nail]

This is done in several formalisms (such as O-Telos - we did some work
on a dialect we called O-Telos-RDF) and also in semantical data models
such as entity relationship diagrams. It is also useful for
reification in general, because you can say something about a
statement by referring to its statement ID.

Wolfgang

> #g
> 
> 
> -------------------
> Graham Klyne
> <GK@NineByNine.org>
Received on Tuesday, 25 June 2002 16:53:02 GMT

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