W3C home > Mailing lists > Public > public-rdf-wg@w3.org > November 2012

Re: B-scopes

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 14 Nov 2012 11:32:21 +0000
Message-ID: <50A38145.4040906@epimorphics.com>
To: public-rdf-wg@w3.org


On 14/11/12 11:02, Richard Cyganiak wrote:
> Following recent discussions, I've written up a proposal to change the design of blank nodes in RDF by explicitly introducing scoped blank node identifiers into the abstract syntax.
>
> http://www.w3.org/2011/rdf-wg/wiki/User:Rcygania2/B-Scopes
>
> Requirements:
>
>  Consistency with all resolutions the WG has made so far
>  No changes to other specs beyond Concepts and Semantics required
>  No changes to conforming implementations required
>
> All further details are in the wiki.
>
> Comments welcome.
>
> Best,
> Richard
>

The idea may be OK although adding a new piece of terminology to explain 
other unclear concepts may not achieve what you hope for.

Comments:

I have no idea what a "blank node scope" is.

[[
There is a widely held misconception in the RDF community that graphs 
cannot share blank nodes. This stems from the fact in practice they 
rarely do and almost never need to,
]]

Any systems that has the default query graph as the union of named 
graphs is sharing bnodes across graphs.

Such systems are not 'rare'.

... sharing ...
[[
but (for the time being) not between graph stores.
]]

The skolemization note makes this confusing.  While not strictly at odds 
with it, the appearance of skolemization suggests global bnodes.


Alternative for consideration:

1/ Make clear that parsing produces a new blank nodes every time for the 
same label.

2/ Talk about "fresh blank node" and not the universal 
not-quite-arbitrary set of blank nodes.

3/ Bnodes are global.

Then the "b-scope" and "bNode = (b-scope, label)" is an implementation 
approach.

	Andy
Received on Wednesday, 14 November 2012 11:33:14 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:25:52 GMT