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Re: Why blank nodes?

From: Steve Harris <steve.harris@garlik.com>
Date: Fri, 7 Sep 2012 12:08:03 +0100
Cc: "public-rdf-wg@w3.org WG" <public-rdf-wg@w3.org>
Message-Id: <FE50F8CB-D790-4A25-86CC-15CB2DD3EBC9@garlik.com>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>
On 2012-09-07, at 11:41, Antoine Zimmermann wrote:

> Le 07/09/2012 12:35, Steve Harris a écrit :
>> Taking a step back, and thinking about what we (Experian) actually use bNodes for, to inform our position on the various scope questions.
>> 
>> Basically, it's just a replacement for auto_increment columns in SQL.
>> 
>> There are two motivations for this
>> 
>> 1) it saves the data generating process from minting a globally unique identifier for it
>> 2) it's more efficient in the store, as there's no need to store a text symbol for it
>> 
>> This has been helped by Skolem URIs, as now we have an easy way to refer to them between SPARQL queries.
>> 
>> Any other features of bNodes are just a distraction or inconvenience really.
>> 
>> I'm sure other people have different reasons for using them, anyone care to share?
> 
> 
> Bnodes are an absolute requirement for OWL to be serialised in RDF. Without bnodes, it would be impossible to define an RDF-based semantics for OWL which is (mostly) compatible with the direct semantics.

What feature of bNodes makes the true though - that's what I was trying to get to.

> Bnodes are very often used to express n-ary relations.

Yup, for reasons 1) and 2) above, IMHO.

> rdf:List without bnodes would be insane.

Right, that's mostly a syntactic thing.

- Steve

-- 
Steve Harris, CTO
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Received on Friday, 7 September 2012 11:08:33 GMT

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