W3C home > Mailing lists > Public > www-rdf-logic@w3.org > July 2002

Re: Dataypes, literals, syntax

From: Jonathan Borden <jonathan@openhealth.org>
Date: Mon, 29 Jul 2002 11:01:12 -0400
Message-ID: <072801c23710$c9ce2550$0a2e249b@nemc.org>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, "pat hayes" <phayes@ai.uwf.edu>
Cc: <www-rdf-logic@w3.org>

pat hayes wrote:

> ... We can get the same effect by
> using a bnode and an extra triple, in effect writing the typed
> literal as a triple:
>
> Jenny age _:x .
> _:x xsd:integer "10" .
>
> >  > As an example of a problematic inference, consider whether
> >>
> >>  <foo://bar> ex:property xsd:integer"10" .
> >>  <foo://baz> ex:property xsd:octal"12" .
> >>
> >>  should or should not entail
> >>
> >>  <foo://bar> ex:property _:xxx .
> >>  <foo://baz> ex:property _:xxx .
> >>
> >>  and how this could be detected by a reasoner.
> >

I am not sure that

Jenny age xsd:integer"10" .

is effectively different than:

Jenny age _:x
_:x xsd:integer "10" .

Indeed:

1) RDF would have to have special knowledge of builtin datatypes to enable
the inference:

<foo://bar> ex:property _:x1
_:x1 xsd:integer "10" .

<foo://baz> ex:property _:x2
_:x2 xsd:octal "12" .

> >>  should or should not entail

<foo://bar> ex:property _:xxx .
<foo://baz> ex:property _:xxx .

so aside from making Ntriples have a more compact syntax -- at the expense
of a whole bunch of otherwise unrequired triples -- it seems that solutions
resulting in a combinatorial triple explosion are popular among so called
triple minimalists :-)

aside from that, what is the difference? In order to get the obvious
entailment, RDF would need to "know about" datatypes, but isn't that the
point about datatypes that knowing the datatype allows you to _do something_
with that knowledge?

otherwise do you suggest that we try to derive all of mathematics, well all
of natural number theory, from RDF triples, and this might be the RDF
datatypes solution? --- you know where that argument is going :-)) --
otherwise how do we represent the notion of "equality"? Am I missing
something?

>
> I guess I disagree. I see no clear upsides, and several downsides.
> Chiefly, I see extra syntactic complexity in the basic spec, for no
> real advantage in expressiveness or efficiency. Basically, small
> constant factors in numbers of triples are not worth bothering with.

Well Ok, but where is the knowledge of how to compare datatype values to
reside? In the intrinsic characteristics of triples?

How will:

foo bar _:x1 .
_:x1 baz "10" .

be different from:

foo2 bar _:x2 .
_:x2 xsd:decimal "10" .

unless RDF has magic knowledge of the URIreference which "xsd:decimal"
represents.

Is teaching RDF about numbers really this complicated?

Jonathan
Received on Monday, 29 July 2002 11:07:26 GMT

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