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From Andy Seaborne <a...@apache.org>
Subject Re: [RDF] Local Scope and BlankNode internalIdentifier (was: github Commons RDF vs. Apache Commons Sandbox RDF)
Date Tue, 03 Feb 2015 16:44:20 GMT
On 03/02/15 15:42, Reto Gmür wrote:
> Should BNode be shareable across Graphs? The Abstract Syntax says that they
> can be shared across the graphs of the same dataset,

Yes - they can be shared.

The note about shared across the graphs of the same dataset is to 
highlight an important point. It is not limiting though.

Other important cases: subgraph, composite graphs (union, intersection etc).

It follows from the definitions but because it's by the lack of any text 
making restrictions, the dataset is explicitly picked up.  The 
definitions build up to graphs from below ... rdf term -> triples -> 
graphs -> datasets. There is no back linkage, no context, in the data model.

(data model = abstract syntax but "abstract syntax" leads to a bit of 
confusion, where as people seem more comfortable with "data model" 
because there are real syntaxes (Turtle, et al).

> What we don't need:
> - A mean for application to re-create identical BNodes (implementations may
> however do so), if we have a pointer to the BNode that's fine, otherwise we
> get existing BNode by accessing the triples in the graph.

A graph is not limited to one JVM (in time or space).

So an implementation may need to create a specific bNode (a database 
would do this, so would transfer

It depends a bit on the "A" in API -- whether "application" means "user 
application" or includes system-machinery things like parsers but the 
boundary is nit easy to fix.

It might include algorithms spread over many machines, they need to 
transfer abstract syntax around.

	Andy




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