- From: Thomas Baker <tom@tombaker.org>
- Date: Wed, 2 May 2012 08:23:34 -0400
- To: Pat Hayes <phayes@ihmc.us>
- Cc: Dan Brickley <danbri@danbri.org>, Sandro Hawke <sandro@w3.org>, public-rdf-wg <public-rdf-wg@w3.org>
On Tue, May 01, 2012 at 11:12:48PM -0500, Pat Hayes wrote: > > The Layers metaphor fits very nicely with the notion of Levels in the FRBR use > > case as described at [1]: > > > > This proposal views descriptions of WEMI entities as bundles of statements > > made at different levels of abstraction, from the most concrete Item level > > to the most abstract Work level. > > Hmmmm. Sorry to be a bit of a pooper, but this worries me. When Sandro + > Danbri came up with the "levels" terminology, I hated it because it suggested > that a "vertical" dimension between layers was meaningful and even important, > which it isn't. It has no semantic meaning at all: the 'layers' have no > intrinsic ordering, and in fact are best thought of as constituting a set > rather than a sequence or list. Yes, I agree! I was assuming that any "order" between levels would be determined by rules specific to the interpretation of (in this case) FRBR -- rules orthogonal to the graphs (or layers) themselves. > But Sandro calmed me down by saying, no, its > just that they are transparent, like sheets of celluloid. But my worry has > now reared its head again, because WEMI "levels" really do have a vertical > order, and one that is semantically significant (level of abstraction). As I see it (which is how the question was framed when we discussed it on 11 April [1]) the question is: where does the semantics of graphs (or layers) end, and the semantics of rules overlaid on those semantics -- I think someone called this "magic," as a placeholder -- begin? [1] http://www.w3.org/2011/rdf-wg/meeting/2012-04-11 > If we endorse this kind of usage, I am afraid that others will start using the > "depth" of a "layer" to mean time sequence, where deeper means older; and > others to mean importance, where deeper means less trusted; and others to > mean all kinds of other things. Which just re-creates the kind of confused > ad-hocery that we have now. I completely agree. > Its OK to use layers to handle levels, supported by a suitable ontology > maybe, but what I DONT want us to even hint at doing is to encourage people > to use some kind of ordering of layers based on an implementation accident or > something meaningless like lexical ordering of the "graph names" to encode > anything meaningful. Absolutely - not even a hint. But by analogy, has there been a problem with implementers reading significance into the order of triples in an RDF dataset? Tom -- Tom Baker <tom@tombaker.org>
Received on Wednesday, 2 May 2012 12:24:10 UTC