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Re: Proposal: variables, templates, and Stickey Cyber Molecules

From: Tim Berners-Lee <timbl@w3.org>
Date: Wed, 17 Jan 2001 22:28:37 -0500
Message-ID: <020d01c080fe$bf63c850$ba01a8c0@CREST>
To: "Seth Russell" <seth@robustai.net>
Cc: "RDF-IG" <www-rdf-interest@w3.org>

----- Original Message -----
From: "Seth Russell" <seth@robustai.net>
To: "Tim Berners-Lee" <timbl@w3.org>
Cc: "RDF-IG" <www-rdf-interest@w3.org>
Sent: Wednesday, January 17, 2001 3:40 PM
Subject: Re: Proposal: variables, templates, and Stickey Cyber Molecules

> Tim Berners-Lee wrote:
> > It isn't enough, when you extend RDF to a langauge of logical formulae,
> > you simple identify which idenmtifiers are variables.  You also have to
> > connect
> > a variable to its scope.  (This is because "for all x there exists y
> > that..." is very different from "there exists y such that for all x...")
> But why do we necessarily need only these kinds of "formula" that make
claims of
> existence?  I intended the expression to mean something more like "if you
> find a set of entities that satisfy this formula, then those are what is
> talked about".

Oh, that sounds like an anonymous node. This is just an existentially
quantifiued variable.

<> foo:replyTo [ foo:writtenBy
    [ foo:mailbox  <mailto:seth@robustai.net> ; foo:firstname "Seth" ]

which you can read as "This document is a reply to something which
was written by that which has email address mailto:seth@robustai.net
and first name "Seth". Maybe that is what you mean.

When you are not doing full logical expressions, then this ability toi refer
something by its properties is all you need.  RDF givges you that with
anonymous nodes, N3 with [].

> [...]  The log:forAll works perfectly for logical formula.   But
> why is it necessary for designating  specific instances of things?

It isn't.  But if you designate something by its proiperties, there is an
implcit "forSome".  For some person whose email address is ....
RDF doesn't make that explicit in the model, only in the syntax.


> Seth Russell
Received on Wednesday, 17 January 2001 22:28:57 UTC

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