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Re: first draft on ISSUE-25 (Deprecate Reification)

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 15 Apr 2011 20:10:25 +0100
Cc: Pat Hayes <phayes@ihmc.us>, RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <472C8DBD-FC8A-460F-A164-3D14DA518C0C@cyganiak.de>
To: Sandro Hawke <sandro@w3.org>
Hi Sandro,

On 12 Apr 2011, at 18:54, Sandro Hawke wrote:
> I wonder if we're close to some succinct consensus text about RDF
> reification, now.    

What is the purpose of writing this text?

I am not in favour of including text like this in any of the REC documents. It is clutter. Readers of those RECs want to know how RDF 2013 works. They don't want to know what's wrong with some legacy feature from RDF 2004.

I would rather prefer to see some discussion of what should be used instead of reification in new applications of RDF.


> Something like:
>        In logic languages, include RDF, "reification" is a
>        sophisticated and error-prone technique where instead of
>        asserting knowledge about some domain of discourse, one asserts
>        knowledge about expression of the language itself.    While
>        reification can be useful, is is often misunderstood and is easy
>        to misuse.   With the latest RDF specifications (@@@tbd), new
>        mechanisms are provided which provide similar functionality to
>        reification but in a more direct and safe manner.  We recommend
>        in nearly all cases these alternatives be used instead.
>        Some of the problems with RDF 2004 reification include:
>        * Confusion about whether two RDF statements with the same
>        subject, predicate, and object are the same statement.   (In RDF
>        2004, they are not.)
>        * No standard way to gather RDF statements together to form RDF
>        graphs.
>        * Referential transparency (instead of opacity), which can lead
>        to surprising results in the presence of inference.  For
>        example, if statements are made about a particular triple
>        (S,P,O) and a reasoner determines S=SS, then it is
>        (counter-intuitively) licensed to infer those statements are
>        also true about triple (SS,P,O). 
>        * Inefficiency: using a straightforward implementation, 3-6
>        times as many triples are needed to enable referring to existing
>        triples.
>        * Potential for paradoxical or ill-defined meaning of
>        oddly-formed and self-referential constructs
> How's that for a start?      Obviously some of this is going to need to
> be refined once we figure out what's really happening with GRAPHS.
>     -- Sandro 
Received on Friday, 15 April 2011 19:10:56 UTC

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