Subject: [MMUSIC] RID Open Issue 3: Escaping in Extension Parameters

From: Adam Roach <[email-masked]>
Date: Mon, 2 Nov 2015 13:42:36 +0900

The parameters on an “a=rid:” line are extensible. The syntax for these is:

    rid-param-other = 1*(alpha-numeric / "-") [ "=" param-val ]
    param-val = *( %x20-58 / %x60-7E ) ; Any printable character except 
semicolon

If an extension has values that can contain semicolons, they need an 
escaping mechanism. Note that this is not an issue for any currently 
defined parameters, as they all take numeric values only.

 1. Change extension syntax to only allow numeric values
 2. Define a universal escaping mechanism for all extensions to use
 3. Leave this problem for the first extension parameter – if any – to
    define value in a way that might allow a semicolon

Thoughts?

/a mmusic-rid.pptx mmusic-rid.pptx

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From: Peter Thatcher <[email-masked]>
Date: Sun, 1 Nov 2015 20:45:28 -0800

I like #3.  It's hard to know what escaping would make sense without
knowing what we'll be escaping.  Let's cross that bridge when we come to
it.

On Sun, Nov 1, 2015 at 8:42 PM, Adam Roach <[email-masked]> wrote:

> _______________________________________________
> mmusic mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mmusic
>

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 2 Nov 2015 14:05:55 +0900

> knowing what we'll be escaping.  Let's cross that bridge when we come to

I was wondering if this really works for unknown attributes. It appears 
that it might, as long as you require comprehension of all attributes in 
an a=rid line. But, I have to note, that a peer that don't support 
escaping will wrongly delimit the line, and interpret what ever is after 
a ";" as a new rid attribute name? Thus, one parsers needs to be 
handling this as case of syntax invalid line, and skip it until you have 
upgraded and supports the escaping.

So, it appear to work, but it is dependent on that one maintain 
"required to understand" for all attributes. I find it ugly, but I will 
likely not be able to propose a solution in the next 3 weeks.

Cheers

Magnus
>
> On Sun, Nov 1, 2015 at 8:42 PM, Adam Roach <[email-masked]
> <mailto:[email-masked]>> wrote:
>
>         param-val = *( %x20-58 / %x60-7E ) ; Any printable character
>     except semicolon
>
>     [email-masked] <mailto:[email-masked]>
> -

-- 

Magnus Westerlund

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