[OK?] Re: Ambiguity of NIL Token

On Fri, May 12, 2006 at 10:25:03AM -0400, Chimezie Ogbuji wrote:
> 
> This is regarding the following SPARQL Grammar rules and query (from the 
> DAWG test data/SyntaxFull/syntax-lists-05.rq):
> 
> [29] ArgList ::= ( NIL | '(' Expression (',' Expression )* ')' )
> [39] Collection := '(' GraphNode+ ')'
> [56] BrackettedExpression ::= '(' Expression ')'
> [85] NIL ::= '(' WS* ')'
> 
> SELECT * WHERE { ( ( ) ) }
> 
> It's not clear how to interpret the NIL token in the above query.  It's 
> not an empty collection or an empty bracketed expression since both of 
> these 'must' have content in between the parentheses.

I read this as a Collection of a NIL. Here's a LALR(1) trace of that query:

http://www.w3.org/2005/01/yacker/uploads/SPARQL?markup=html&lang=perl&text=SELECT+*+WHERE+%7B+%28+%28+%29+%29+%7D&action=validate+text


85 says that NIL may have 0 or more whitespace characters betweek the
parentheses, i.e. no content.


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> Chimezie Ogbuji
> Lead Systems Analyst
> Thoracic and Cardiovascular Surgery
> Cleveland Clinic Foundation
> 9500 Euclid Avenue/ W26
> Cleveland, Ohio 44195
> Office: (216)444-8593
> ogbujic@ccf.org

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Received on Thursday, 1 June 2006 11:19:29 UTC