- 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 15:14:03 UTC