- From: Pat Hayes <phayes@ihmc.us>
- Date: Mon, 12 Nov 2012 11:49:14 -0600
- To: Richard Cyganiak <richard@cyganiak.de>
- Cc: RDF Working Group WG <public-rdf-wg@w3.org>
On Nov 12, 2012, at 9:48 AM, Richard Cyganiak wrote: > Hi Pat, > > On 12 Nov 2012, at 08:29, Pat Hayes wrote: >>> Allocating a *fresh blank node* is the action of drawing a new node from the set. >> >> I don't think that last sentence makes sense. How does one perform an action on a set? And what counts as a "new" element of a set? Sets don't live in an operational space where things happen to them at times. > > Think of it as: “Allocating a fresh blank node is the action of making a new mark on a surface.” That makes sense. Drawing a node from a set does not make sense, or at any rate, it raises more questions. Is the drawn node still in the set after the drawing, for example? (I bet many readers will assume it is not...) Why do you need this sentence at all? What expository purpoese does it serve? > > Works now? > >>> [[ >>> Since RDF systems generally refer to blank nodes only via such local identifiers, it is necessary to “standardize apart” the blank node identifiers when incorporating data that originates from an external source. This may be done by systematically replacing the blank node identifiers in incoming data with freshly allocated blank node identifiers. >> >> Unfortunately, this idea of standardizing apart applies to the blank nodes themselves, not just to their identifiers. > > Hm. > >> (Because there is nothing in the curent abstract RDF model that prevents two distinct graphs from "accidentally" sharing a blank node.) > > I'm trying to understand. Can you give an example where we end up with two distinct graphs that “accidentally” share a blank node? You explained this very well yourself in another email message to the LOD list: http://lists.w3.org/Archives/Public/public-lod/2012Nov/0014.html The point is not that there are examples where this happens, so much as there is nothing in the specs to prevent it happening, so you can't just assume that it doesn't. For all we know, there could only be a few thousand blank nodes that get re-used over and over again. Pat > > Best, > Richard > > > >> We could fix this problem by changing the abstract structure of graphs and blank nodes along the lines suggested in http://www.slideshare.net/PatHayes/rdf-redux, but this would require us to take a nontrivial action and make a nontrivial change to RDF, so it is unlikely to happen :-) Barring this, it is misleading to imply that standardizing apart (and the distinction between unioning and merging) is only of concern to bnode identifiers. >> >> Pat >> >>> ]] >>> >>> >>> I believe this resolves ISSUE-107, hence I'm marking it PENDINGREVIEW. >>> http://www.w3.org/2011/rdf-wg/track/issues/107 >>> >>> Best, >>> Richard >>> >> >> ------------------------------------------------------------ >> IHMC (850)434 8903 or (650)494 3973 >> 40 South Alcaniz St. (850)202 4416 office >> Pensacola (850)202 4440 fax >> FL 32502 (850)291 0667 mobile >> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes >> >> >> >> >> >> > > > ------------------------------------------------------------ IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Monday, 12 November 2012 17:49:50 UTC