- From: Orri Erling <erling@xs4all.nl>
- Date: Tue, 31 Mar 2009 08:47:05 +0200
- To: "'Chimezie Ogbuji'" <ogbujic@ccf.org>, "'Seaborne, Andy'" <andy.seaborne@hp.com>, "'Lee Feigenbaum'" <lee@thefigtrees.net>
- Cc: "'Kjetil Kjernsmo'" <Kjetil.Kjernsmo@computas.com>, "'RDF Data Access Working Group'" <public-rdf-dawg@w3.org>
-----Original Message----- From: public-rdf-dawg-request@w3.org [mailto:public-rdf-dawg-request@w3.org] On Behalf Of Chimezie Ogbuji Sent: Tuesday, March 31, 2009 1:24 AM To: Seaborne, Andy; Lee Feigenbaum Cc: Kjetil Kjernsmo; 'RDF Data Access Working Group' Subject: Re: Querying "all graphs" I've created two features: - http://www.w3.org/2009/sparql/wiki/Feature:CompositeDatasets - http://www.w3.org/2009/sparql/wiki/Feature:AllNamedGraphs CompositeDatasets is meant to be a comprehensive solution for composing named, arbitrary subsets from all named graphs in a dataset, while AllNamedGraphs is supposed to be 'low hanging fruit' (i.e., the feature that there seems to be more consensus need around and corresponds to Lee's #1). Chimezie The usefulness of this is quite clear. We have always queried the set of the graphs when no default graph was specified. More recently we have added a way to have a single name stand for an enumerated collection of graphs. There is a way of also querying all graphs except a specified list. If we are looking at an open web situation where each graph is a personal foaf file, then some access control or reliability filtering will generally be needed. This means qualifying the graph by some query, for example consider only graphs from people I know. Such things can be expressed if the graph is initially the union of everything and then restricted pattern by pattern. Like select * where graph <directory> { ?g has_author <me>} . graph ?g { <me> foaf:knows ?x }} This would be all the people I know according to me. The directory graph would be just a regular graphkeeping graph origins and maintained by application logic. Listing graphs as enumeration of literals is a bit easier to optimize even though the equivalent can be expressed as above. Orri
Received on Tuesday, 31 March 2009 06:48:33 UTC