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Re: Layers

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 30 Apr 2012 13:50:13 -0500
Cc: public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <28D2B3DC-AA8A-4318-AF26-E0552E97065D@ihmc.us>
To: Sandro Hawke <sandro@w3.org>
This is VERY like the 'surfaces' proposal in http://www.slideshare.net/PatHayes/rdf-redux (see especially slides 7-10), but with one very important difference: surfaces cannot share bnodes with other surfaces. As this aspect of the surfaces design was critical to making bnodes work more rationally and providing a notion of bnode scoping, I wonder if it is worth debating this point in more depth. Can we combine these ideas in some way? A surface is something like a bundle of overlaid layers, like a movie still made up from overlaid cels. Or, put the other way, a layer is part of a suface which has been peeled off and raised above the surface. (Danbri's pictures work either way.) Think of the surface as the opaque background of the transparent layers: bnodes are marks on this surface. We could copy a layer onto another surface, for example, and then the suface idea of conjunction (replacing unions and merges) works here also: to conjoin A and B, just copy them both onto a new surface. 

It is worth trying to get this right, as we are tantalisingly close to making RDF have full first-order expressiveness here. The 'codices' idea (later slides) is very much like layers sitting on top of a surface, but beause of the bnode scoping, it effectively provides for nested quantification, which layers wouldnt be able to do by themselves. BUt the closeness of the intuitions is striking.

Even if this is beyond charter for this WG, I would like to think about it, if only to make sure we don't accidentally do something that would accidentally block this as a future extension for some trivial careless reason. 


On Apr 29, 2012, at 2:41 PM, Sandro Hawke wrote:

> It all makes sense to me now.  It's so simple: 
>        http://www.w3.org/2011/rdf-wg/wiki/Layers
> Dan Brickley's suggestion of the term "layer" instead of "named graph"
> fit so well for me, it made this all flow nicely.   I suspect this is
> what many people think of when they say "named graph" -- I just couldn't
> get past all the other meanings of that term.
> Hopefully you'll all like my three examples, which I think cover the
> territory of use cases pretty well.
>     -- Sandro

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Received on Monday, 30 April 2012 18:50:44 UTC

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