Re: [apps-discuss] draft-yevstifeyev-abnf-separated-lists-00.txt

[Tony Hansen <[e-mail]>]

On 12/6/2010 11:11 AM, Mykyta Yevstifeyev wrote:
> Hi all,
>
> Some answers:
>>>> Your draft is inconsistent. In one place, you use "m" and another 
>>>> place
>>>> you use "o".
>>>>
>>>> I don't see why you use "o" at all -- I recommend you just use "m".
>>> o = m-n as m is maximum and n we have already used as it is mimimum.
>>> So we can use only he differebce between them.
>>
>> We *can*, but that doesn't mean we *should*.
>>
>> Other ABNF constructs use "m" and "n" directly -- they do *not* use 
>> the difference.
>>
>> I think using the difference for this case is just asking for trouble 
>> and will introduce subtle errors in future protocols that use this 
>> construct.
>>
>> Consider the normal 5234 ABNF rule <a>*<b>element. <a> is the minimum 
>> and <b> is the maximum. It is *not* <a>*<b-a>element.
>>
>> The 822 ABNF rule <a>#<b>element, which your rule is updating, also 
>> used the same minimum and maximum values -- it did *not* use the 
>> difference.
> However we MUST use *n* elements and MAY use all more *(m-n)*. If we 
> say that we use the we MAY use more *m*, it is possible that we use 
> *(m+n)* togetger, but we MUST use at most *m* while
> *m+n is not m*

m+n is not m, nor is m-n. The second number that is used is the * and # 
rules is not how many more are allowed beyond the minimum, but really is 
the maximum. That is, 2*3 and 2#3 mean a minimum of 2 and a maximum of 3 
-- it's not a minimum of 2 plus possible 3 more for a maximum of 5.

This rule should do likewise.

>> Note also: your introduction is incorrect. It talks about ABNF having 
>> the # rule. However, it does not. The original 822 ABNF had the # 
>> rule, but it was dropped when ABNF was extracted for the *234 series.
> Maybe I meant the construction form RFC 2616.

That's fine -- say so then.

Note that the #rule in 2616 also uses a minimum of n and a maximum of m 
-- it does not use a difference for the second number.

If you're going to offer this as an update to RFC 5234, you may wish to 
specify that the #rule be added in as well.

     Tony Hansen
     [e-mail]