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

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:


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.


Received on Wednesday, 26 September 2012 16:42:24 UTC