CommentResponse:ST-1

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Sebastian,

Thank you for you message to the SPARQL Working Group. I apologize for not responding before now.

> Looking at named graphs as "just" a fourth node IMHO it makes perfect
> sense to allow templates for graphs in all commands.

Not all graph stores allow for named graphs. SPARQL specifically avoids requiring a "fourth" node, though it is supported. Also, many storage APIs treat graphs as a separate type of entity to a triple, despite the storage mechanisms removing this distinction. For these reasons graphs a necessarily treated differently to the other elements in a "triple".

> A simple example would be:
> 
> drop graph ?g where { ?g <foo> <bar> . }
> 
> But this also applies to insert queries:
> 
> insert { 
>   graph ?g { ?s ?p ?o . }
> }
> where {
>   blabla .
>   ?g foo bar .
> }

SPARQL 1.1 Update has left the issue open as to whether or not a graph store allows empty graphs. Consequently deleting all the elements in a graph *may* result in that graph being deleted as well. This means that your first example can be duplicated on many stores using a DELETE operation. Your INSERT example is already supported explicitly in the spec.


> In the spirit of completeness one could even think of finally completing
> construct queries and allowing for the following:
> 
> construct { graph ?g { ?s ?p ?o . } . graph <foobar> { .... } } where {
> ...... }

This is a worthwhile suggestion and one that has already been considered. However, it requires a result format that supports quads. The working group is required to use a standardized format for results, and currently there is no W3C standard for encoding multiples graphs in a single file. Such standards have been proposed, but will not be available before SPARQL 1.1 is finalized.

> Thus, my question is: is there any good reason against allowing
> templated named graphs in pretty much every command?

CONSTRUCT is a query, rather than an update operation, but your point is made.

Templated graphs already appear in most operations, with the exception of the graph operations: CREATE, DROP, CLEAR and LOAD. LOAD is a unique operation, used for data transfer, and CLEAR is simply a shorthand for a specific DELETE operation. CREATE is redundant and may be useful for graph administration on some systems. Similarly, DROP is a combination operation that both clears a graph and removes it. For systems that do not support empty graphs, CREATE is a no-op and DROP is identical to CLEAR.

Regards,

Paul Gearon