[Versa] Versa issue: subgraph primitives?

[Michael Olson]

On Sep 8, 2005, at 9:16 PM, Chimezie Ogbuji wrote:

>> { type(rss:item) - rss:title -> contains('4Suite') } . - dc:creator  
>> -> *
>>
>> or
>>
>> { type(rss:item) |- rss:title -> contains('4Suite') } . - dc:creator  
>> -> *
>
> Whoops, the use of '.' to refer to the context bound to the scoped
> query doesn't seem right.  I'd probably want:
>
> { type(rss:item) |- rss:title -> contains('4Suite') } [ - dc:creator  
> -> *]
> or
> { type(rss:item) |- rss:title -> contains('4Suite') } all() -  
> dc:creator -> *
>
> Since, '.'  refers to the context 'node' (as of the current
> specification).  In this case, the 'context node' as it was defined
> before is actually a list of statements (in the new sense), so it
> doesn't seem to make sense in the first slot of a traversal expression
> - which expects a list of 'resources' (not statements) to match
> statement subjects against.
>
> That's probably not clear, but basically, introducing a context (a
> named list of statements) as a first class object means you have to
> account for every possible place it could be used in the grammar.
>

I missed that as well.  However, WRT your concerns of the new data  
type, I don't see it as any different then having to check for

6 - rdf:value -> *

(assuming 6 is a constant, not a literal query)


> And just for the record.  I'm pretty sure (at least in the RDBMS
> implementation of a context-aware RDF store) that
>
> { type(rss:item) |- rss:title -> contains('4Suite') } all() -  
> dc:creator -> *
>
> would be more efficient to execute than
>
> (type(rss:item) |- rss:title -> contains('4Suite'))  - dc:creator -> *
>

I agree.  In 4RDF, I see an extension function for its idea of scope so

subgraph c = ext:subgraph-by-scope("http://4Suite.org")
{c} query

where the processor could be very smart and not evaluate "c" because it  
s just an addition to the where clause later....

*slap* premature optimization.....

Mike

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Mike Olson                                                Principal  
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