- From: Sandro Hawke <sandro@w3.org>
- Date: Fri, 23 Sep 2011 11:13:47 -0400
- To: Satya Sahoo <satya.sahoo@case.edu>
- Cc: Graham Klyne <GK@ninebynine.org>, public-rdf-prov@w3.org, W3C provenance WG <public-prov-wg@w3.org>, Andy Seaborne <andy.seaborne@epimorphics.com>
On Thu, 2011-09-22 at 10:40 -0400, Satya Sahoo wrote:
> Hi Sandro and Graham,
>
> On Thu, Sep 22, 2011 at 2:09 AM, Graham Klyne <GK@ninebynine.org>
> wrote:
> On 21/09/2011 23:27, Sandro Hawke wrote:
> [cc'ing public-prov-wg, but reply-to set to
> public-rdf-prov, where as I
> understand it this discussion should proceed.]
>
> On Wed, 2011-09-21 at 16:49 +0100, Graham Klyne wrote:
> ..........
>
> might be considering.
>
> The resulting requirement that we articulated
> was that for the purposes of
> provenance, we must be able to treat two
> "named" graphs with identical graph
> content as two distinct entities.
>
> ...
>
> The use-case is this:
>
> Suppose we have some resource R.
>
> Observer A makes a provenance assertion about
> R on Monday 2011-09-19, which is
> expressed as an RDF graph Pra
>
> Observer B makes a provenance assertion about
> R on Friday 2011-09-23, expressed
> as RDF graph Prb
>
> To express provenance about the provenance
> assertions, we may wish to say:
>
> Pra statedBy A; onDate "2011-09-19" .
>
> Prb statedBy B; onDate "2011-09-23" .
>
> It may be that the provenance assertions Pra
> and Prb have identical content;
> i.e. they are RDFG graphs containing identical
> triple sets. For the purposes of
> provenance recording, it is important that
> even when they express the same
> graphs, Pra and Prb are distinct RDF nodes.
> If Pra and Prb are treated as a
> common RDF node, one might then infer:
>
> _:something statedBy A ; onDate "2011-09-23" .
>
> which in this scenario would be false.
>
> Isn't this just some modeling confusion? Pra and Prb
> are each an event
> of the authoring of a statement (ie they are
> "statings"), not
> statements, based on how you use them, giving them
> dates and such.
> Those two statings can then be connected to the same
> statement (graph,
> G1).
>
> Pra statement G1; dc:creator A; dc:date "2011-09-19".
> Prb statement G1; dc:creator B; dc:date "2011-09-23".
>
> Then G1 can just be a literal, or whatever we use to
> allow conversations
> about g-snaps.
>
>
> Yes, this is indeed a modelling choice. As I note later, I
> wasn't dismissing the graph literal approach, just trying be
> expose the need, which might be addressed in different ways.
>
>
> I am a bit confused here - originally Graham used Pra and Prb as "an
> RDF graph", so they can be treated as resources and we can make
> statements about it - creator and date.
I don't agree. RDF graphs are pure mathematical objects, like the
number 7. It doesn't make sense to give the number 7 a date. When he
gave it a date, it became clear to me that he had to be talking about
something else.
> Also, the "event" will be the equivalent to a PE "statementMaking" and
> the output will be Pra and Prb.
Sorry, I'm missing some context here, but "statementMaking" sounds right
for what Pra and Prb are -- there the event of making a statement, not
the statement (graph) itself.
> I agree with Sandro that Graham's original use of Pra and Prb maps
> them to g-snaps from RDF WG terminology. Looking at the definitions of
> g-box and g-snap, they almost seems to be a class-instance
> correspondence between them?
Hmmm, I don't see anything class/instance like. In programming terms,
a g-snap is like the number seven and a g-box is like a memory location
which might, at some point in time, hold a bit pattern representing the
number seven. Or a g-snap is like a words "Back in 5 minutes" and a
g-box is like a door where you sometimes hang a sign with those words.
We need both these concepts because URLs name g-boxes but the
information we actually see and work with is packaged into g-snaps (or
serializations of g-snaps).
-- Sandro
>
>
> .....
>
> A particular consequence of this is that an
> RDF "named graph" specification
> based on graph literals (where RDF literals
> are self-denoting), somewhat like
> formulae in Notation 3, would have to be used
> with care. That is, if Pra and
> Prb are graph literals, then Pra = Prb, and
> the given provenance-of-provenance
> statements could not be expressed as suggested
> above.
>
> It seems to me Pra and Prb are not g-snaps (RDF
> graphs), so there's no
> problem here.
>
>
> Again, an interaction of modelling and design choices. There
> *could* be a problem, depending on what choices are made.
>
>
> Again, Pra and Prb seem to fit the definition of g-snap?
>
>
> Best,
> Satya
>
>
> #g
> --
>
>
>
> (This does not preclude a graph literal
> approach being used, but the above
> use-case might need to be constructed slightly
> differently.)
>
> #g
> --
>
>
>
>
>
>
>
>
Received on Friday, 23 September 2011 15:13:59 UTC