Paul,

> The RDF named graph theory makes a distinction between the main "default" 
> graph and named, child sub-graphs. And the
> implementations e.g. NG4Java take this simple one-level hierarchy approach. 

There is no "default" graph and any graph's hierarchy in NG4J. All NamedGraphs 
in NamedGraphSet are independent (from each other) graphs within the same 
document. I supposed to use the plane NamedGraphSet in the following approach:
1.SubContext has an access to the triplets of its graph only.
2. "root" Context has an access to the triplets of all graphs in the document.

> I think we should consider support for sub-contexts to be something that CPs 
> can optionally support. So I think we
> need some kind of API to ask a CP what its "level" of sub-context support is. 
> [I can't remember if we have any method
> in IdAS along these lines already--indicating what "optional" features of 
> IdAS interfaces are or are not supported by
> any given CP implementation. Sergey?]

No, we do not have such a method.

If you do mean IExtension interface added into IdAS API by Jim, 

(the following IContext methods use it: 
public Iterator getEntities(String query, Iterator attrSelectionList, 
IExtension[] extensions)
public String open(IAuthNMaterials authentication, IExtension[] extensions) 
)

I do not see how we can use it for SubContexts. 

Thanks,
Sergey Lyakhov

On Wed, 26 May 2010 09:25:14 -0400
Paul Trevithick <[email protected]> wrote:

> Ideally we wouldn't. The problem is implementation. 
> 
> The RDF named graph theory makes a distinction between the main "default" 
> graph and named, child sub-graphs. And the
> implementations e.g. NG4Java take this simple one-level hierarchy approach. 
> 
> So if we do decide to allow arbitrary nesting in the Context Data Model (as 
> represented by the IdAS interfaces) we'd
> still have to deal with the fact that context providers (like the NG4Jena 
> one) couldn't implement it. Which is
> doable--we'd just insist that CPs declare what level of support they have for 
> this stuff. For example:
> 
>       * support for n-levels of sub-Contexts
>       * support for one-level of sub-Context (e.g. the NG4Java CP)
>       * no support for sub-Contexts
> 
> I think we should consider support for sub-contexts to be something that CPs 
> can optionally support. So I think we
> need some kind of API to ask a CP what its "level" of sub-context support is. 
> [I can't remember if we have any method
> in IdAS along these lines already--indicating what "optional" features of 
> IdAS interfaces are or are not supported by
> any given CP implementation. Sergey?]
> 
> On May 26, 2010, at 8:41 AM, Mike McIntosh wrote:
> 
> > I know this seems obvious to those of you that are elbow deep in this stuff 
> > but…
> > Why do we want to prevent sub-contexts of sub-contexts?
> >  
> 


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