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Re: [Turtle] the Turtle Grammar in the revised editor's draft does not allow comments in Turtledoc

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Tue, 08 Mar 2011 18:32:43 +0000
Message-ID: <4D76764B.1090902@epimorphics.com>
To: Alex Hall <alexhall@revelytix.com>
CC: public-rdf-wg <public-rdf-wg@w3.org>

On 08/03/11 17:57, Alex Hall wrote:
> On Tue, Mar 8, 2011 at 12:28 PM, Antoine Zimmermann
> <antoine.zimmermann@insa-lyon.fr
> <mailto:antoine.zimmermann@insa-lyon.fr>> wrote:
>     The grammar at http://www.w3.org/2010/01/Turtle/#prod-turtle2-WS has
>     a token called "PASSED TOKENS" which defines comments in Turtle, but
>     it cannot be reached from the root "turtleDoc".
>     It should be included in the <WS> token definition, I guess.
> I interpret that to mean that comments are recognized as tokens, but
> skipped by the lexer (i.e. not passed to the parser).  Of course that
> assumes an implementation that splits recognition into lexing and
> parsing stages -- I'm not aware of other types of recognizers but that
> doesn't mean they aren't out there.
> -Alex

yes - [[Section 4.2 Comments
Comments are treated as white space.

like SPARQL, it's assumed they are removed at a low level, as tokens are 
formed.  Tools, e.g. javacc, and many other, can skip or hide comments.

White space (production ws) is used to separate two tokens which would 
otherwise be (mis-)recognized as one token.

Then the parser itself does not specify whitespace directly,

[6]    	triples 	   ::=    	subject predicateObjectList

does not say <WS>* after 'subject'.  There would be a lot of <WS>* 
padding and you still have to talk about misrecognized tokens and it 
would not fit many tool chains.

I think "PASSED TOKENS" is a reflection of the tool chain Eric was using 
as indicated by it's rule name of [-].

Received on Tuesday, 8 March 2011 18:33:21 UTC

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