Re: [Slim] Ticket #26 Make use of the asterisk modifier on media level with session scope also for media level purposes

[Randall Gellens <[e-mail]>]

At 5:40 PM +0000 6/8/17, Natasha Rooney wrote:

>  The additional text describing the * has not been added and myself 
> and Bernard are unsure of how the current text is sufficient. Can 
> you add some text or let us know how this is already covered? 
> Thanks!
>
>  See comment 8 and 9 to see the request in the ticket.
>
> 
> <https://trac.ietf.org/trac/slim/ticket/26>https://trac.ietf.org/trac/slim/ticket/26

The text describing the use of asterisk was modified in the more 
recent updates of the draft.  I am not aware of any remaining 
ambiguity.

Specifically, Section 5.2 contains:

    In an offer, each list of language tags MAY have an asterisk appended
    at the end.  An asterisk appended to any value in any media in an
    offer indicates a request by the caller to the callee to not fail the
    call if there is no language in common.  See Section 5.3 for more
    information and discussion.

While Section 5.3 contains:

    A consideration with the ability to negotiate language is if the call
    proceeds or fails if the callee does not support any of the languages
    requested by the caller.  This document does not mandate either
    behavior, although it does provide a way for the caller to indicate a
    preference for the call succeeding when there is no language in
    common.  It is OPTIONAL for the callee to honor this preference.  For
    example, a PSAP is likely to attempt the call even without an
    indicated preference when there is no language in common, while a
    call center might choose to fail the call.

    The mechanism for indicating this preference is that, in an offer, if
    the last token of any 'hlang-recv' or 'hlang-send' value for any
    media is an asterisk, this indicates a request to not fail the call.
    The called party MAY ignore the indication, e.g., for the emergency
    services use case, regardless of the absence of an asterisk, a PSAP
    will likely not fail the call; some call centers might reject a call
    even if the offer contains an asterisk.

The examples in Section 5.5 show an asterisk used in some cases.

Additionally, Section 6.1 contains:

    Attribute Syntax:

       hlang-value =  Language-Tag *( SP Language-tag ) [ SP asterisk ]

                            ; Language-Tag as defined in BCP 47

       asterisk    =  "*"   ; an asterisk (0x2A) character

       SP          =  1*" " ; one or more space (0x20) characters

Which makes it clear that an asterisk may be appended to the list of 
language tags, and that it can only appear at the end.

-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
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Virtue has never been as respectable as money.      --Mark Twain