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Re: RDF PATCH and Downstream consequences of blank nodes [was Re: SPARQL Profile for PATCH]

From: Ronald P. Reck <rreck@rrecktek.com>
Date: Thu, 25 Sep 2014 15:40:30 -0400
Message-ID: <54246FAE.7080903@rrecktek.com>
To: semantic-web@w3.org
+1 FWIW, I believe this sums up my own feelings on the topic incredibly 
well. At least I am not the only one that feels this strongly about it.
Thank you David for this.

-Ronald P. Reck


On 09/23/2014 05:34 PM, David Booth wrote:
> BTW, I want to draw attention to the fact that the need for defining an
> RDF-specific PATCH operation is *entirely* a consequence of RDF's
> allowance of unrestricted blank nodes.  I do not think that blank nodes
> should be eliminated from RDF, but I am convinced that RDF's current
> treatment of blank nodes is a significant design flaw that has *many*
> downstream effects that are ultimately detrimental to RDF's adoption.
> The need for RDF PATCH is another example.
>
> Unix/linux diff and patch utilities have been used successfully for
> *decades*, with many other information representations.  Imagine how
> simple and easy it would be if we could just generate canonical
> N-Triples and use standard diff and patch against that!  But we can't,
> because blank nodes are unstable across RDF serializations and no
> canonical way to generate them has been standardized.  This, in turn is
> because generating a canonical form of unrestricted RDF is a hard
> problem (NP-complete), because of blank nodes.  The problem is *much*
> easier if the use of blank nodes is limited to *implicit* blank nodes --
> those that are generated implicitly by the use of square brackets "[]"
> or parentheses "()" for lists in Turtle -- and indeed this is the vast
> majority of blank node use.  (See "Everything You Always Wanted to Know
> About Blank Nodes", by Hogan, Arenas, Mallea and Polleres:
> http://www.websemanticsjournal.org/index.php/ps/article/viewFile/365/387 )
>
> For this reason the use of "Well Behaved RDF" was proposed, which limits
> the use of blank nodes to implicit blank nodes:
> http://dbooth.org/2013/well-behaved-rdf/Booth-well-behaved-rdf.pdf
> I don't know if Well Behaved RDF is the best solution to this problem.
> Maybe someone will come along with a better idea.  But I am convinced
> that the current treatment of blank nodes in RDF is a serious problem
> that we should fix in order to make RDF simpler to use, understand and
> adopt.
>
> I really don't like having to make excuses for RDF when it cannot be
> used in a similar way as nearly every other information representation
> -- such as being able to easily compare two RDF documents for "equality"
> (which in RDF becomes a complex graph isomorphism problem) or generate a
> simple diff and patch -- all because of RDF's unrestricted treatment of
> blank nodes.
>
> Clearly this is not something that the Linked Data Platform working
> group can fix.  But I think it is important to bring it to people's
> attention, in the hope that we will someday soon have the creativity and
> gumption to fix it.
>
> I should also acknowledge that there are some who do not feel that RDF's
> treatment of blank nodes is a problem.  Fine.  It may not be a problem
> to an elite few who are well steeped in the subtleties of description
> logic, model theory and RDF Semantics, and who don't mind having to use
> RDF-specific tools instead of generic tools.  But having tried for over
> 10 years to explain RDF to a wider audience of regular software
> developers, I am convinced that subtleties like RDF's treatment of blank
> nodes *are* a problem to a much wider audience of *potential* RDF users
> who would be more inclined to adopt RDF if it didn't have complexities
> like this.  As it is they are more likely to stick with JSON or XML,
> whose complexities they already know, rather than venturing into the
> obscure and esoteric world of RDF.
>
> RDF tools are not as mature as those for XML or even JSON, which is much
> younger than RDF.  I believe blank nodes are one specific reason they're
> not.  The fact that we still don't even have a simple, standard way to
> compare RDF documents and compute diffs and patches, is a perfect example.
>
> David
Received on Thursday, 25 September 2014 19:41:06 UTC

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