- From: Peter Frederick Patel-Schneider <pfps@research.bell-labs.com>
- Date: Wed, 20 Apr 2011 13:55:25 -0400
- To: <alexhall@revelytix.com>
- CC: <public-rdf-wg@w3.org>
From: Alex Hall <alexhall@revelytix.com> Subject: Re: SPARQL update with blank nodes Date: Wed, 20 Apr 2011 12:48:24 -0500 > On Wed, Apr 20, 2011 at 1:36 PM, Peter Frederick Patel-Schneider < > pfps@research.bell-labs.com> wrote: > >> So now I don't understand SPARQL 1.1 Update, which states >> >> Deleting triples that are not present, or from a graph that is not >> present will have no effect and will result in success. *Using a new >> blank node in a delete template will lead to nothing being deleted, as >> the new blank node cannot match anything that already exists.* >> [emphasis added] > > A better way of phrasing that might be, "a blank node label in a delete > template may not be reliably assumed to denote any particular resource > in the > graph." Well, this is different, but, because it is different, I wouldn't call it a better phrasing, but instead ... "different". The document uses "matching", and the only "matching" around for blank nodes in triples is RDF instance matching. >> because blank nodes *do* match, as per SPARQL 1.1 query. > > Blank nodes in the WHERE pattern act as local variables that match > anything, > but are projected out of the result set. > > A better comparison is probably to blank nodes in a CONSTRUCT template, > described here: > > http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#tempatesWithBNodes > > [[ > A template can create an RDF graph containing blank nodes. The blank > node > labels are scoped to the template for each solution. If the same label > occurs > twice in a template, then there will be one blank node created for each > query > solution, but there will be different blank nodes for triples generated > by > different query solutions. > ]] I don't see where this bit has anything in common with matching. > -Alex peter
Received on Wednesday, 20 April 2011 17:56:26 UTC