Re: RDF API

Janne,

in my understanding RDF nodes cannot exist independently of the arcs
they are hanging on. In this sense, the semantics of set operations is
straight-forward:

> For example: remove a model of one triple (A,B,C) from model (A,D,E).
> Is the result an empty model or one single node E?
> 
> Or: what is the intersection of (A,B,C) and (A,D,E)?

{(A,B,C)} minus     {(A,D,E)} = {(A,B,C)}
{(A,B,C)} intersect {(A,D,E)} = {}
{(A,B,C)} union     {(A,D,E)} = {(A,B,C), (A,D,E)}

etc.

Thus, removing and adding nodes, i.e. specific resource URI, to the
model is not necessary.

However, thinking more about the core API, I'm tending to say that the
set-oriented view on RDF models may be not appropriate in some
circumstances. For example, if your models represent datasources a la
Mozilla, it arguably may not make sense to intersect an email folder
with a file system directory.

The question is whether is it reasonable to reduce the core API even
further, to remove union, intersection and difference and to place them
into a separate interface that extends the core Model.

Sergey