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

Re: Reification thing questions

From: Seth Russell <seth@robustai.net>
Date: Mon, 4 Feb 2002 21:14:34 -0800
Message-ID: <014501c1ae04$00234c20$657ba8c0@c1457248a.sttls1.wa.home.com>
To: "Pat Hayes" <phayes@ai.uwf.edu>
Cc: "RDF-LOGIC" <www-rdf-logic@w3.org>
From: Pat Hayes (phayes@ai.uwf.edu)
see: http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Feb/0107.html

Let me take a shot at these:

> Further to my last message, let me suggest some key questions to ask
> about the things that a reification is supposed to describe, ie what
> _:x is intended to denote when we write

>   _:x  <rdf:type>      <rdf:Statement> .
>   _:x <rdf:subject>   <subject> .
>   _:x <rdf:predicate> <predicate> .
>  _:x  <rdf:object>    <object> .

It could denote an actual appearance of the triple in some document, at some
time, authorship, etc ...
But the actual node you mention above says nothing about an appearance, so
the example is kind of skew.  A better example of an appearance of a triple
would include at least one other predicate about the appearance.

Also the node above could occur in a entailment rule ... such and such a
statement entails such and such other statement.    (<=> (instance ?CLASS
Class) (subclass ?CLASS Entity))  If we had the audacity to code that into
RDF, then the two subordinate clauses would be coded like the _:x node you
coded above.  [And, yes I know, your not supposed to do that in RDF].

>1.  Does it make sense to say that _:x has properties like date it
>was asserted, who wrote it, where it was imported from?


>(If not, just to be awkward, what if someone actually asserts
>such properties of _:x? Does something complain, or is that
>just a kind of  inconsistency?)

If not, then there is a lot of RDF out there with this kind of

>2.  If there is only one of these things, where is it? Does that
>question make sense?

If the thing to which you refer is the thing denoted by the node identified
with _:x above, then it must needs occur in some RDF document.  But there
are probably many of those occurrences, not just one. So if there must be
only one of them, then maybe it would be the ideal triple in the sky .. and
your answer is in Plato's Heaven .... but I hope that is not the way it will
go down.

>If not, what kinds of question would make sense applied to the thing?

... who said it, in what document, how much one trusts it, what might entail
it, what it might entail, is it true, is it false, is it a lie, do you like
it ... stuff like that.

>3. Can the thing be located in an RDF graph?

Both the thing denoted (the appearance of a triple) and the thing denoting
(the node you quoted above) are located in RDF graphs .. though not always
the same graph at the same time.

>If so, and if that graph is in a document (with a URI),
>is the  thing in the document?

Depends: one document could be describing the occurrence of a triple in
another document or in the same document.

>(Could it be accessed via the URI?)

I don't know how to do that.

>If the document is copied, is the thing in the graph also copied?


>If so, is the copy of it [some] other thing or is it the same thing?

It's some other thing.

>If another, does it also satisfy the description  in the reification above?

Depends on how precisely the description is qualified.

For example:

foo:bar goo:dar poo:sar.

rdf:type rdf:Statement;
rdf:subject foo:bar;
rdf:predicate goo:gar;
rdf:object: poo:sar;
ex:time "9:15PM"
email::mid  0$657ba8c0@c1457248a.sttls1.wa.home.com ;
ex:documentLocation  :SethsOutbox

The description above describes the triple as it existed momentarily in my
out box.  It does not describe the copy of that same triple as it exists in
your inbox.

Well,  how did I do?

Seth Russell
Received on Tuesday, 5 February 2002 00:17:52 UTC

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