Re: [Slim] Open Issues on draft-ietf-slim-negotiating-human-language

[Randall Gellens <[e-mail]>]

At 2:00 PM +0000 6/1/17, Natasha Rooney wrote:

>>  On 1 Jun 2017, at 14:49, Randall Gellens 
>> <<mailto:[e-mail]>[e-mail]> 
>> wrote:
>>
>>  The syntax does not permit a * only, there has to be at least one 
>> language tag.
>>
>
>  That's fine - but can we just explain that somewhere?

We do.  Section 5.2 says:

    In an offer, each value MAY have an asterisk appended as the final
    value.  An asterisk appended to either value 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.

Section 5.3 says:

    The mechanism for indicating this preference is that, in an offer, if
    the last value of any 'hlang-recv' or 'hlang-send' 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.

Section 6.1 says:

    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

So, the text in both 5.2 and 5.3 make clear that an asterisk may be 
appended, but can't appear on its own.  The text also explains what 
an asterisk means.  The syntax in 6.1 also clearly shows that an 
asterisk can only appear after one or more language tags.

(As a separate issue, Gunnar felt that using the word "value" to mean 
the set of language tags as well as each language tag or asterisk is 
confusing, so I'm thinking I will use the word "token" for the second 
use, to refer to each tag or asterisk.)
-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
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Never look at the trombones, it only encourages them.
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