Re: [Slim] Ben Campbell's Yes on draft-ietf-slim-negotiating-human-language-22: (with COMMENT)

Randall Gellens <rg+ietf@randy.pensive.org> Wed, 10 January 2018 16:12 UTC

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Date: Wed, 10 Jan 2018 08:12:29 -0800
To: Ben Campbell <ben@nostrum.com>, "The IESG" <iesg@ietf.org>
From: Randall Gellens <rg+ietf@randy.pensive.org>
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Subject: Re: [Slim] Ben Campbell's Yes on draft-ietf-slim-negotiating-human-language-22: (with COMMENT)
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At 8:21 PM -0800 1/9/18, Ben Campbell wrote:

>  I'm balloting "yes" because I think this is important work, but I have some
>  comments:
>
>  Substantive Comments:
>
>  - General: It seems to be that this is as much about human behavior as it is
>  capabilities negotiating. Example case: I make a video call and 
> express that I
>  would like to receive Klingon. (Is there a tag for that ? :-) The callee can
>  speak Klingon and Esperanto, so we agree on Klingon. What keeps the 
> callee from
>  speaking Esparanto instead?

There is a language tag for Klingon: "tlh".

The draft is not trying to even capture the full complexity of human 
language interaction, much less enforce it.  The draft provides a 
fairly simple mechanism to make it more likely that successful 
communication can occur, by identifying language needs (which can 
allow endpoints to take potentially required additional steps, such 
as bridging in translation or relay services, or having a call 
handled by someone who known the language(s) or can use the needed 
media).

>  I realize we can't force people to stick to the negotiated languages--but
>  should we expect that users should at least be given some sort of 
> UI indication
>  about the negotiated language(s)? It seems like a paragraph or two on that
>  subject is warranted, even if it just to say it's out of scope.

I will add to the Introduction the following text:

    This document does not address user interface (UI) issues, such as if
    or how a UE client informs a user about the result of language and
    media negotiation.


>  -1, paragraph 6:  (related to Ekr's comments) Does the selection of a single
>  tag in an answer imply  an assumption only one language will be 
> used? There are
>  communities where people tend to mix 2 or more languages freely and 
> fluidly. Is
>  that sort of thing out of scope?

Earlier versions of the draft had more explicit text that the draft 
did not attempt to capture the full range of human language issues, 
including the common practice among multilingual people of mixing 
languages.

The draft currently says:

    (Negotiating multiple simultaneous languages within a media stream is
    out of scope of this document.)

There was text in a version of the draft as of February 2013 that said:

    (While it is true that a conversation among multilingual people often
    involves multiple languages, it does not seem useful enough as a
    general facility to warrant complicating the desired semantics of the
    SDP attribute to allow negotiation of multiple simultaneous languages
    within an interactive media stream.)

I do not recall the reasons why the text was simplified, removing 
mention of multilingual people, and would have to search through 
minutes of the various WG sessions and email in 2013 where the draft 
was discussed.  I suspect there was desire to have the draft merely 
state what it does and doesn't do, and not get into a lot of value 
judgment discussion.


>  - 5.1, paragraph 2:  Can you elaborate on the motivation to have a separate
>  hlang-send and hlang-recv parameter vs having a single language parameter and
>  instead setting the stream to send or receive only, especially in 
> light of the
>  recommendation to set both directions the same for bi-directional language
>  selection? I don't mean to dispute that approach; I just think a bit more
>  explanation of the design choice would be helpful to the reader.  I 
> can imagine
>  some use cases, for example a speech-impaired person who does not 
> plan to speak
>  on a video call may still wish to send video to show facial expressions, etc.
>  (I just re-read the discussion resulting from Ekr's comments, and recognize
>  that this overlaps heavily with that.)

As you suggest, a media might be desired in both directions even 
though only one direction is primarily intended for interactive 
communication.  The draft currently says:

    When a media is intended for interactive communication
    using a language in one direction only (e.g., a user with difficulty
    speaking but able to hear who indicates a desire to send using text
    and receive using audio), either hlang-send or hlang-recv MAY be
    omitted.  When a media is not primarily intended for language (for
    example, a video or audio stream intended for background only) both
    SHOULD be omitted.  Otherwise, both SHOULD have the same value.  Note
    that specifying different languages for each direction (as opposed to
    the same or essentially the same language in different modalities)
    can make it difficult to complete the call (e.g., specifying a desire
    to send audio in Hungarian and receive audio in Portuguese).

I will add "Note that the media can still be useful in both 
directions."  The text thus becomes:

    When a media is intended for interactive communication
    using a language in one direction only (e.g., a user with difficulty
    speaking but able to hear who indicates a desire to send using text
    and receive using audio), either hlang-send or hlang-recv MAY be
    omitted.  Note that the media can still be useful in both directions.
    When a media is not primarily intended for language (for example, a
    video or audio stream intended for background only) both SHOULD be
    omitted.


>  -5.1, paragraph 3: "... which in most cases is one of the
>     languages in the offer's..."
>  Are there cases where it might not?

Yes, it could happen.  For example, if an emergency call comes into a 
PSAP and requests languages that the PSAP is unable to support, the 
PSAP will likely want the call to proceed anyway.  It's also possible 
that the callee might support a language that has some degree of 
mutual comprehensibility to those requested by the caller.  An 
example might be some Scandinavian languages where the caller does 
not include a language that is similar enough to have some 
comprehension but not be fluent enough to include in the UE 
configuration.


>  -5.1, last paragraph: "This is not a problem."
>  Can you elaborate? That sort of statement usually takes the form 
> "This is not a
>  problem, because..."

The caller and callee are free to use any of the established media 
streams.  If a caller requests audio, video (with a sign language), 
and text, and all three are established, the caller might ignore the 
text or audio stream and use only the video stream.

>  -5.2, last paragraph: Is there a reason to give such weak guidance on how to
>  indicate the call is rejected?  (Along those lines, are non-SIP 
> uses of SDP in
>  scope?)

No one made a case for why mandating a particular rejection code was 
necessary, especially since the draft does not offer any suggestion 
as to if a call should proceed or fail when there aren't mutually 
supported languages.

>
>  Editorial Comments and Nits:
>
>  -5.1, paragraph 4: The first MUST seems like a statement of fact.

You mean this sentence:

    In an offer, each value MUST be a list of one or more language tags
    per BCP 47 [RFC5646], separated by white space.

The MUST makes sure that the values are IANA-registered language tags.

-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
-------------- Randomly selected tag: ---------------
The first rule is, you must not fool yourself.  And you are the
easiest person to fool.                       --Richard Feynman