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Putting metadata in the "default" graph Re: Dataset Syntax - checking for consensus

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Wed, 26 Sep 2012 12:41:57 -0400
Message-ID: <50633055.1010508@thefigtrees.net>
To: David Wood <david@3roundstones.com>
CC: W3C RDF WG <public-rdf-wg@w3.org>
On 9/26/2012 12:09 PM, David Wood wrote:
> * Some designs for carrying for metadata
>
> PROPOSED: In our dataset syntax, we'll say that metadata goes in the default graph
> +0.5, especially if it can be aligned with SPARQL service descriptions.
>
>

What do existing systems do when importing a TriG file that contains 
data in the "default" graph? The Anzo store has /no default graph/, and 
therefore either throws an error or throws away any information in a 
TriG "default graph". Similarly, all TriG exported from Anzo does not 
have a default graph /unless /it's the serialization of a SPARQL RDF 
dataset (which//by definition does have a default graph, of course).

I bring this up because I brought up a related thread on 
public-sparql-dev recently:

http://lists.w3.org/Archives/Public/public-sparql-dev/2012JulSep/0025.html

In that thread, I asked:

"""
Do all quad stores  / named graph stores include a default graph? If the 
store that you develop or use does have a default graph, does that graph 
also have a name (URI)?
"""

The answers were:

Anzo -- no default graph (except ones assembled on the fly for querying).
OWLIM -- has a default graph with no URI
RDF::Query -- has a default graph with no URI
4store & 5store -- default graph is a view on existing graphs (& 
therefore, I assume, doesn't exist for purposes of /storing /data) -- 
uses a "special" named graph for writing default data
TDB -- can either have an actual default graph or just use the default 
graph as a view onto the other named graphs

Additionally, there was input from 3 implementers (SteveH, GregW, and 
Chime) that if they could re-implement their systems they would not 
include a default/unnamed graph.

All of which is to say, I think there's a fair amount of evidence that 
the "default" or unnamed graph is not consistently used, and perhaps not 
widely used. We need to support it for compatibility, but I think it's a 
mistake to specify that anything important be put in that graph.

Lee
Received on Wednesday, 26 September 2012 16:42:24 GMT

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