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Re: New public version of RDF Model and Syntax Draft Specification

From: Pasqualino \ <assini@kamus.it>
Date: Tue, 28 Jul 1998 00:42:50 +0200
Message-ID: <35BD026A.E2E8E03E@kamus.it>
To: "Ralph R. Swick" <swick@w3.org>
CC: www-rdf-comments@w3.org
First of all, I want to thank you for your extremely kind and thorough
answer.

The accuracy and open mindness with which you evaluate external comments
it's for me the best guarantee of the high quality of your work. 

Now to go back to business ...

Ralph R. Swick wrote:

> [...]
> The schema designer can say, as you suggest, that there is
> no semantic difference between having a collection as a property
> value and having repeated property values.  Other schema designers
> will want to be able to recognize the grouping given by collections
> as semantically significant.  This was the intent of Section 3.4
> to show a motivating example for delaring a difference.
> [...]
> OK; do you feel that such a distinction is never going to be useful
> to any schema designer?  Perhaps we need to work harder to find a
> motivating example for this differentiation.  On the other hand,
> you might wish to convince us that any such need would be so small
> that the additional complication in RDF to give schema designers
> this flexibiilty is unjustifiable.  I do welcome your further remarks.

So the real question is: should repeated property values be allowed in
RDF ? 

As the expressive power of the language wouldn't be compromised, as
there is nothing that can be expressed with repeated values that
couldn't be expressed with a Bag, I wonder why we shouldn't simply get
rid of repetitions.

The current presence of two very similar mechanisms in the language has
the unintended consequence of obliging every schema writer to operate a
choice between the two (and to oblige every reader of his/her data to be
aware of the choice he/she made).

As you perfectly know, in technical matters it's almost never required
to find a new solution to a given problem but rather to operate a choice
among the many existing solutions.

Whatever goes in the direction of simplifing this choice it's a step in
the right direction.  

It's not by chance if many of the most successful languages in existence
(C and Java being notable examples) are basically a simplification of
previous languages.

What these languages offer it's a reduction in superficial flexibility
without renouncing to the essential expressive power.

This is also the case of XML. The "added value" that XML provides with
respect to SGML is nothing but the reduction in (mostly) useless SGML
syntax flexibility.

But, for most applications, XML is still too much flexible in the sense
that, to express a certain semantic, you are still left with too many
possible choices.

That's exactly why people will be drawn to RDF.

They will like the fact that it offers a "pre-canned" semantic model
that radically reduces the number of useless choices that they have to
make to devise a semantic schema.

What they are looking for in RDF is not "flexibily" but constrains,
constrains to guide the process of determining an appropriate syntax to
convey the semantic they want to express.


-- 
Pasqualino "Titto" Assini  ---  assini@kamus.it  
Kamus Internet Consulting  ---  http://www.kamus.it/
Received on Monday, 27 July 1998 20:16:01 GMT

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