[Versa] More on literal queries

[Michael Olson]

>> Just to be clear, your not talking about a "context" as shown in the
>> above EBNF correct?  In the EBNF, context is the ".".  I've been  
>> trying
>> to talk about the "scope" of an expression which I think is what you
>> mean.
>
> I should be explicit.  When I said context, I mainly meant the idea of
> a subgraph (possibly named).  But there are three interpretations, as
> I see it:
>

So, lets try and give them names that are not so confusing.

> - Context:  A named subgraph In the pure RDF sense (the scope
> attribute on 4RDF Statements)
>

Scope.

> - Versa Context:  Consisting of a core data type, variable bindings,
> namespace declarations, and a named Context (subgraph)
>

Context.

> - The '.' Expression: Shorthand for the the data type instance
> associated with the current Versa Context
>

This can be "current" from the XPath spec.

> So, { .. } would be a 'Context expression' which resolves to an
> anonymous Context (subgraph), which will then be associated with the
> Versa context used to evaluate the scoped expression that follows in:
>
> { .. } <scoped expression>
>
> That sound about right?
>

Yep

Mike

>>>
>>> statement(subj,pred) => set(stmt1,stmt2,..stmtN)
>>> where stmt1 ... stmtN all have subj as their subject and pred as  
>>> their
>>>
>
>> Something like that.  I was thinking it would look just like the
>> filter/traverse functions (take three arguments) and instead of
>> returning a set of subject, or set of objects, would return the entire
>> statement.  So we have (with functions) the ability to get a set of
>> subject, a set of objects and a set of statements.  Then, the  
>> following
>> expression would be equivalent
>>
>> subject(statements(all(),*,*))  == filter(all(),*,*)
>> object(statements(all(),*,*,*)) == traverse(all(),*,*)
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Mike Olson                                                Principal  
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