- From: Ivan Herman <ivan@w3.org>
- Date: Mon, 10 Oct 2011 15:03:25 +0200
- To: Sandro Hawke <sandro@w3.org>
- Cc: public-rdf-wg <public-rdf-wg@w3.org>
- Message-Id: <DA8B4D12-1421-4CF3-9408-B8AF76EAC407@w3.org>
Sandro, I need clarifications on 'R'. I presume 'R' is a time interval. Does it mean that for any dataset to be valid, a time interval should be defined for it? I guess we can say that if there is no such 'R' as part of a dataset definition, it is considered to be... undefined? 'All Time'? How does this affect deployed datasets that may have G-s that vary in time already, but where there is no such time definition? Should we require SPARQL 1.1 to have a function that returns 'R' for a given dataset? I wonder whether we can shy away from mentioning time altogether and accept that fact that <N,G> refers to a name for a G-box, ie, to something that can change over time, and our spec remain silent on this... Ivan On Oct 10, 2011, at 13:30 , Sandro Hawke wrote: > Here's some revised wording for the proposal, getting a bit closer to > spec text. It's still somewhat informal, and mixing normative and > non-normative bits, and best-practice. And it's not as clear as it > should be about handling change over time. > > -- Sandro > === > A dataset D is true iff (1) its default graph is true and (2) for > every pair of <N,G> in D, N names something (a "resource", sometimes > called a "g-box") which, at every time T in R, has G as its current > state. > > It follows from AWWW that if N is an IRI which can be dereferenced, > a successful, correct dereference of N at any time T in R must yield > a serialization ("representation") of G. > > In order to know whether a dereference occurs at a time in R, it is > useful to have R declared in the default graph of D, or in another > nearby, easy-to-find data source. Where possible, is is helpful to > have R be All Time; that is, having N name a resource whose state, > by definition, never changes. > > In RDF data, N may be used (1) directly, to name the g-box, > expressing things like the license that applies to its state, or who > controls it; and (2) indirectly, to refer to G as the current state > of the g-box. Indirect reference can be used to express things > about an RDF Graph (a "g-snap"), like that it was the graph some > entity asserted at some time. Indirection is done in the semantics > of the predicates with which N is used. > > When N is used indirectly, the reference to G only holds inside time > range R, of course. Care must be taken not to use N as if it > necessarily referred to G, outside of R. Since R is defined to be > the same for all elements of D, indirect reference is safe in the > default graph. > > > > ---- Ivan Herman, W3C Semantic Web Activity Lead Home: http://www.w3.org/People/Ivan/ mobile: +31-641044153 PGP Key: http://www.ivan-herman.net/pgpkey.html FOAF: http://www.ivan-herman.net/foaf.rdf
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Received on Monday, 10 October 2011 13:02:26 UTC