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Re: ABNF switch: list rules

From: Mark Nottingham <mnot@mnot.net>
Date: Sun, 25 May 2008 09:44:47 +1000
Cc: ietf-http-wg@w3.org
Message-Id: <CCFD9C14-1823-4DB6-9CCF-515A7B033D2C@mnot.net>
To: "Frank Ellermann" <hmdmhdfmhdjmzdtjmzdtzktdkztdjz@gmail.com>

I disagree; I've seen implementations produce empty elements, and  
"it's ugly" isn't a good enough reason to break them.

That's not to say that we shouldn't discourage it. Also, we have an  
open issue about whether line folding should be disallowed;
   http://tools.ietf.org/wg/httpbis/trac/ticket/77


On 25/05/2008, at 2:02 AM, Frank Ellermann wrote:

>
> Julian Reschke wrote:
>
>> Is there consensus for this?
>
> No.  #-LWS has to be killed or obsoleted.  ASCII art by commas
> is only ridiculous, but "apparently empty lines" are dangerous.
> Example, #x permits...
>
> ,,,   ,   ,   ,,,  <CRLF>
> ,  ,  ,   ,  ,     <CRLF>
> ,,,   ,   ,  , ,,, <CRLF>
> ,  ,  ,   ,  ,   , <CRLF>
> ,,,    ,,,    ,,,  <CRLF>
>
> ...and that's IMNSHO ugly.  But it also permits...
>
> ,,,,,,,,,<CRLF>
> <SP>      <CRLF>
> <HTAB>    <CRLF>
> ,,,,,,,,,<CRLF>
>
> ...and that is dangerous when applications don't get the subtle
> difference between "really empty" <CRLF> and "apparently empty"
> <SP><CRLF> or even <HTAB><CRLF> lines.
>
> The ABNF has to be very obvious what is permitted, and what is
> obsoleted, without misguided attempts to hide these horrors in
> any #-constructs.

Yes, which is why we should address the LWS issue first.


--
Mark Nottingham     http://www.mnot.net/
Received on Saturday, 24 May 2008 23:45:29 GMT

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