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Re: Well Behaved RDF - Taming Blank Nodes, etc.

From: David Booth <david@dbooth.org>
Date: Wed, 12 Dec 2012 14:47:53 -0500
To: Ivan Shmakov <oneingray@gmail.com>
Cc: semantic-web <semantic-web@w3.org>
Message-ID: <1355341673.2301.6721.camel@dbooth-laptop>
On Thu, 2012-12-13 at 01:04 +0700, Ivan Shmakov wrote:
> >>>>> David Booth <david@dbooth.org> writes:
> 
> […]
> 
>  > For example, one key limitation would be in the use of blank nodes,
>  > which severely complicate what could otherwise be simple tasks, such
>  > as comparing two RDF graphs for equality.  With unrestricted blank
>  > nodes, this becomes a difficult graph isomorphism problem instead of
>  > a simple text comparison.  Some have suggested eliminating blank
>  > nodes entirely, but a more modest restriction would be to limit them
>  > to common idioms that do not cause such complexity problems:
> 
>  > A Well-Behaved RDF graph is an RDF graph that can be serialized as
>  > Turtle without the use of explicit blank node identifiers.  I. e.,
>  > only blank nodes that are implicitly created by the bracket "[ ... ]"
>  > or list "( ... )" notations are permitted.
> 
> 	My suggestion would be to only disallow cycles composed entirely
> 	of blank nodes.
> 
> 	As it seems, an RDF graph following this restriction could be
> 	“canonicalized” quite easily, . . . .

Yes, that is pretty much my intent, but I thought it would be easier to
explain (to casual RDF authors) by defining it in terms of avoiding the
need for explicit blank node identifiers in Turtle.  Otherwise we would
have to get into the details of defining what is a blank node tree and
how it relates to the RDF graph, which seemed harder to explain.  But I
could be wrong.



-- 
David Booth, Ph.D.
http://dbooth.org/

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Received on Wednesday, 12 December 2012 19:48:27 UTC

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