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More syntax issues

From: Jack Jansen <Jack.Jansen@cwi.nl>
Date: Thu, 26 Mar 2009 15:22:52 +0100
Message-Id: <6AC72378-DE6F-427A-BF97-BC41996A4E48@cwi.nl>
To: Yves Lafon <ylafon@w3.org>
Cc: Media Fragment <public-media-fragment@w3.org>
Another possible issue with the syntax:
xywhunit allows "%" or "pixel" as production, and since xywhunit  
itself is optional, this gives us the following ways to specify  
spatial fragments (ignoring aspect, for now):

	xywh=10,20,30,40
	xywh=pixel:10,20,30,40
	xywh=%:10,20,30,40

The last one looks weird: if I'm reading this I'm expecting a percent- 
escaped string but it isn't. According to our grammar there's no  
problem (pct-encoded isn't allowed here) but I can imagine that it  
could lead to implementation problems (if people do percent-escape  
processing on the URL early). I think I would be in favor of spelling  
out "percent".

A somewhat related issue is with utf8string (in addition to the more  
serious issue with single quote I noted in a previous mail): because  
it consists of a sequence of pchar it is allowed to use sub-delims in  
there. My fragment parser starts by splitting the fragment on '&',  
then splitting the results of these on '=', then parsing the resulting  
(prefix, value) lists with regular expressions. This failed when I got

	id='a&b'

Again, according to the syntax there is no problem, but for  
implementations we might make life easier if inside utf8string we  
would disallow sub-delims.
--
Jack Jansen, <Jack.Jansen@cwi.nl>, http://www.cwi.nl/~jack
If I can't dance I don't want to be part of your revolution -- Emma  
Goldman
Received on Thursday, 26 March 2009 14:23:33 GMT

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