W3C home > Mailing lists > Public > www-rdf-interest@w3.org > May 2004

Re: less-restrictive range and domain terms

From: Benja Fallenstein <b.fallenstein@gmx.de>
Date: Tue, 04 May 2004 20:10:12 +0200
Message-ID: <4097DC84.4010802@gmx.de>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: pdawes@users.sourceforge.net, www-rdf-interest@w3.org

Hash: SHA1

Peter wrote:
|> "There exist triples with property P and an object of class foo," rather
|> than "All triples with property P have objects of class foo," is a
|> useful interpretation, I presume.
| But this is even expressible in RDF (at least for non-datatypes)
|     _:x P _:y .
|     _:y rdf:type foo .

True. If you have a query language, asking for whether there are any ?c
such that

~    ?x P ?y .
~    ?y rdf:type ?c .

isn't even harder than asking whether there are any ?c such that

~    P  rangeIncludes  ?c .

OTOH, if you have a plain "Give me all triples (P, rangeIncludes, _)"
interface, the second is much easier / more efficient than the first
(where you have to iterate through all triples "(_, P, _)").

Phil, does Peter's way of stating this seem useful for what you want to do?

|> | So, show us the inferences!
|> ~    flabber x:schnack ghasted
|> ~    ghasted rdf:type y:Ghostly
|> =====>
|> ~    x:schnack phil:rangeIncludes y:Ghostly
| This is *one* inference.  What about the others?  Are there any?

I'm pretty sure that this is the one inference that Phil meant.
x:schnack has an object of class y:Ghostly; therefore, x:schnack *can*
have objects of class y:Ghostly.

Yes, it's obvious, but it's useful b/c it tells you that it makes sense
to show resources of class y:Ghostly as possible objects for x:schnack
triples (or so I understand Phil).

- - Benja
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Received on Tuesday, 4 May 2004 14:10:57 UTC

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