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Re: Reification - whats best practice?

From: Tom Adams <tom@tucanatech.com>
Date: Fri, 27 Aug 2004 09:18:45 -0400
Message-Id: <9F8A9AA8-F82B-11D8-B3C1-000A95C9112A@tucanatech.com>
To: www-rdf-interest@w3.org

Hi Bob (& others),

Please mail the DAWG comments list: public-rdf-dawg-comments@w3.org 
with your suggestions. We have asked for public feedback, and this is 
precisely what this comments list is for. All comments brought up on 
the list are reviewed regularly by the WG and factored in.

Cheers,
Tom


On 26/08/2004, at 12:32 PM, Bob MacGregor wrote:

>  Steve Harris wrote:
>
> On Wed, Aug 25, 2004 at 10:47:13 -0700, Bob MacGregor wrote:
>
>    Sandro Hawke wrote:
>
>  The right solution is to use contexts.  Contexts can be implemented
>  using quads instead of triples, or by using a scheme for
>  encapsulating groups of statements, as is done in the Triple system.
>  The DAWG committee is taking baby steps towards contexts by
>  including a SOURCE element in BRQL.  If you substitute the term
>  "context" for "source" in a BRQL query, then you have quads.  Some
>  of us are planning to "abuse" BRQL by treating the sources as if
>  they are contexts.  I would not be surprised if members of the DAWG
>  committee have that in mind (but I can't speak for them).
>
> It is still up in the air wether SOURCE will be included, some of the
> members are not keen on it.
>
> - Steve
>
>  It would be sad indeed if this small step forward (SOURCE) doesn't 
> happen. 
>
>  What many seem to be missing is that the notion of a "named container 
> of triples" is common to all solutions
>  that are being argued.  A document of RDF triples is a subcase.  A 
> named graph is a subcase
>  (or the same case).  A reified statement is the subcase where the 
> container can contain only
>  one triple. 
>
>  When someone says "I'm not using contexts, because we can't agree on 
> what they mean, but
>  here is my named container solution", they are really using contexts 
> -- they've just settled
>  on a particular case. 
>
>  The issue of quads is in some sense secondary.  A quad is just the 
> syntactic glue that relates
>  each triple in a container to the container.  So the fundamental 
> issue relates to contexts, not quads.
>
>  So where is the controversy?  Possibly is has to do with the problem 
> of nested contexts.  The
>  most general solutions allow contexts to contain other contexts.  If 
> the named graph solution
>  allows one to apply a name to a subgraph of another graph, then it is 
> supporting exactly the same kind of
>  nesting.  The named document solution does not support nesting.
>
>  Summing up. 
>
>  - The current RDF provides miserable support for provenance data (to 
> cite the
>  most obvious use case for contexts). 
>
>  - Named containers of triples provide a solution.  Many 
> implementations of named
>  containers already exist.
>
>  - Most implementers of triple stores implement some
>  form of container inside their systems to indicate the source of the 
> triples, but RDF
>  doesn't provide a means for them to expose that mechanism.
>
>  - The SOURCE construct in BRQL would provide a solution that is 
> narrower than,
>  but consistent with, a general named container solution.
>
>  My near-term recommendation would be to pester the DAWG committee to 
> include
>  SOURCE in their spec.  Its quite hard to get traction in this area, 
> and that is currently
>  our best shot.
>
>  Cheers, Bob
>
>
> Bob MacGregor
>  Chief Scientist
>
>
> Siderean Software Inc
>  5155 Rosecrans Ave, #1078
>  Hawthorne, Ca 90250
>
> bmacgregor@siderean.com
>
> tel:
> +1-310-491-3424
>
> fax:
> +1-310-491-3338
>
>
>
>  
>
>  
>
>  
>
>  
>
>
-- 
Tom Adams                  | Tucana Technologies, Inc.
Support Engineer           |   Office: +1 703 871 5312
tom@tucanatech.com         |     Cell: +1 571 594 0847
http://www.tucanatech.com  |      Fax: +1 877 290 6687
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Received on Friday, 27 August 2004 13:18:47 UTC

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