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Re: RDFCore last call WD's: Two comments on the RDF documents

From: Frank Manola <fmanola@mitre.org>
Date: Wed, 29 Jan 2003 07:48:24 -0500
Message-ID: <3E37CD98.4020709@mitre.org>
To: Bob MacGregor <macgregor@isi.edu>
CC: www-rdf-comments@w3.org


Thanks for the comments.  I want to clarify your comments on the Primer 
so I can decide the changes that are needed.  My questions follow.

Bob MacGregor wrote:

> In examining the RDFCore documents, I have found two sections where I 
> believe
> the language needs to be rewritten.
> In the excerpt below from the RDF Primer, I believe that the use of double
> brackets in the example is misleading, and should be replaced by 
> something else.
> It illustrates a statement syntactically nested within another 
> statement.  There
> is nothing in the current RDF equivalent to such a construct.  It 
> preceeds a
> discussion of reification, which might lead a reader to believe that RDF's
> notion of a reified statement (a "stating") is somehow related to this 
> kind of
> nesting.
>     RDF Primer
>     4.3 RDF Reification
>     Now, suppose we wanted to say in RDF that this statement was made by 
> John
>     Smith. Since in RDF we can only make statements about resources, 
> what we would
>     like to be able to do is write something like:
>      [[exproducts:item10245  exterms:weight  "2.4" .]] dc:creator  
> exstaff:85740 .

The intent here was to indicate the need to be able to treat a statement 
as a resource, in order to make statements about it, not to indicate 
that we want to support nesting per se (which we don't).  Would a 
diagram (along the lines of Figure 8 in the original Model and Syntax 
spec) be less misleading in your opinion?  Or perhaps eliminating the 
double brackets and say that we want to treat the statement as a 
resource, say by assigning URI "foo" to it, and then illustrate 
statements with "foo" as the subject?

> Here are two quotes from Pat Hayes' emails:
> " ... rather like saying that the
> ability to sing eliminates the need to stand on one foot. Nesting hasn't 
> got
> anything to do with reification."
> "Many people have suggested using reification to simulate expression 
> nesting in
> recursive syntax, but this kind of usage for reification was a mistake 
> from the
> start."
> Pat is claiming that reification and nested statement syntax have 
> nothing to do
> with each other, while the excerpt from 4.3 uses nesting as a lead-in to a
> discussion on reification.  While my personal belief is that there IS a
> connection, I will affirm that nested statements do not correlate with the
> notion of a "stating" that RDF has adopted.  Hence my recommendation that
> the example of nested syntax be replaced by something else.

The intent of the text was to introduce what we would *like* to be able 
to do, not what we actually can do.  The rest of the text describes the 
*intended* interpretation, and then points out that we can't actually do 
that (and this latter discussion is along the lines of what Pat actually 
says in the Semantics document).  Is that discussion not clear, or is it 
just that the apparent "nesting" example at the beginning throws the 
whole discussion off?  Would saying at the beginning that we can't 
actually do those "stating" descriptions using "reification" help?

Thanks again.


Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Wednesday, 29 January 2003 07:29:39 UTC

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