- From: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
- Date: Fri, 30 Sep 2011 15:17:28 +0200
- To: Richard Cyganiak <richard@cyganiak.de>
- CC: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Richard, I can not give you a compelling use case, as obviously, whatever can be achieved by a dataset without default graph can obviously be achieved by a dataset with default graph... But do you have a use case that would be solved by a dataset with default graph, that a dataset *without* default graph would *not* solve? pa second thought: this is not a use case as such, but a personal experienve. The class Graph in the python library rdflib, embeds the notion of namespace prefix. You can write: g = rdflib.Graph() g.bind("foaf", "http://xmlns.com/foaf/0.1/") print g.serialize() I find this utterly annoying, because once I declare a prefix for the sake of one particular serialization, it sticks with my graph forever. I would much prefer: g = rdflib.Graph() prefixes = {"foaf": "http://xmlns.com/foaf/0.1/"} print g.serialize(prefixes) this would, IMHO, be better design, and is a similar problem to the one I see with the default graph. On 09/30/2011 11:37 AM, Richard Cyganiak wrote: > On 29 Sep 2011, at 16:42, Pierre-Antoine Champin wrote: >> A such, I consider the default graph to be a *property of the SPARQL >> engine* used to query the data, rather than a property of the data itself. > > What's the problem with considering the default graph a property of the dataset? > > Use cases, examples, test cases? > > You present your personal opinion, and your preferred solution, and muse about how the non-preferred solution came about historically. I find none of this even remotely compelling unless some practical problems arise from including the concept of a default graph in the RDF spec. > >> Imagine a world where SPARQL would have defined, as part of a dataset, >> the notion of *default resource*, so that I could write >> >> SELECT ?friend WHERE { >> foaf:knows ?friend >> } >> >> Would we feel compelled to include the default resource in RDF Concepts? > > This is a distraction here, but yes, the notion of a specially marked “default resource” (which would likely be the base URI in graphs deployed on the web) would actually be extremely useful because it would provide a natural and unique way of chopping RDF graphs into trees for serialization. > > Best, > Richard
Received on Friday, 30 September 2011 13:18:13 UTC