Re: Comments on SHACL Editors Draft of 29 April

Hi Irene,

On Sun, May 01, 2016 at 11:59:30AM -0400, Irene Polikoff wrote:
> However, fundamentally, SHACL operates under the closed world assumption.
> So, it could never concern itself with whatever exists or doesnąt exist in
> the world in general - it is always only about the information that has
> been been made available/submitted to a SHACL engine. Negation as failure
> and so on.

Sure - I'm completely with you re: CWA.  That was, indeed, the idea
behind the DSP work circa 2007-2008.  

In SHACL, as I picture it (which is not necessarily what the spec says),
CWA should operate with respect to the triples asserted in the graph of
data at hand.

> This could be fixed by saying something like:
> 
>     "Class-based scopes define the scope as the set of all instances of a
>     Class present in the data graph."

Yes, that's better, though in the spirit of a CWA view on a given data
graph, might it perhaps be more precise to refer not to a set of
instances, but to a set of nodes?

> Perhaps, it is worth making a point of explaining this somewhere early on
> and then, there is no need to constantly clarify points like this
> everywhere in the document. If a reader approaches the spec with the OWA
> set of mind, they are bound to make wrong conclusions or become confused.
> Thus, it is important that a reader puts themselves into the CWA set of
> mind.

Yes, I agree - and I agree that it would be worthwhile to make the point
early.  My point, however, is that when the spec says:

  "Class-based scopes define the scope as the set of all instances of a
  class."

it is using the language of RDF Schema. Full stop.  If this is not the
intended meaning (and it shouldn't be), then the spec should use
different words.

Tom

-- 
Tom Baker <tom@tombaker.org>

Received on Sunday, 1 May 2016 17:24:24 UTC