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

Bernard Aboba <> Thu, 11 January 2018 05:07 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id DBC7F12E89E for <>; Wed, 10 Jan 2018 21:07:09 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.698
X-Spam-Status: No, score=-2.698 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id 59wGKtbZA33A for <>; Wed, 10 Jan 2018 21:07:05 -0800 (PST)
Received: from ( [IPv6:2607:f8b0:400c:c05::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id CE2BF12E89B for <>; Wed, 10 Jan 2018 21:07:04 -0800 (PST)
Received: by with SMTP id s139so802816vkb.3 for <>; Wed, 10 Jan 2018 21:07:04 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=VIjyOKM8WC7HXgjnNCrdZjWR5QSlsg8GzOiJ4XkxaZI=; b=pJM6bi+n9g3KnIjwI8FrHrLvOksm58N8Rw2BdOhnZINQyiOfwhGI+2BaTjrIFMlERi +MpBuEgJkRzWXCC6DmdXSOhyIXsZ1VUMSX+N++rnrz8DoJs83EHviU+X3J0iFz0i6X2n wPZTeNuArq9jUAkEiFmAE2G7c4/yDG2naUciUEAXyC4juNKJkwsK7eQy1CvoLb+3pWtH 0w9s3sgCOyGc+qrnBJTQhKrpt+cFxVRMfFiDGCyog/gMn0i3R0JYjdYStr8Yhxbehng0 VTe241ZZJnZQMQdcWVv8JKs1HO2A9maApm8aHkWYAV8YTNHo0hrEMgCY7DnYnSI3Vo06 C2Yw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=VIjyOKM8WC7HXgjnNCrdZjWR5QSlsg8GzOiJ4XkxaZI=; b=MR4XvwsDw/U6gBB8NdBtjZfsdOWa0X72GJX7Ys9O/CCcXxcga40Pg3fqkO6P6/Mey1 LOoTeLwGowa5lGgrbrNT4S6JtbfW3YDaIRcoOIYB9sMx+6/h9uCV7DhOAsqAThV9KzIl q4k+WkH3Yy21L1kR1nEu15GalRTb1n7ykYmp2RTSuYtKvb5Gi0t+inmXoQU/b7P62tQB 4LAIBUKfiestiy5NQ3HDpbkvBTKkVbfMAvb9SXTf+0wD+k99STOTo0qtPu+y9rmcT8ox xTEteoxh88CrJWFeY7mBdGoVNKL/lzjBYJfvPkdvvoP6y41hf5WMJ4/wxVEGpmqflph5 p8zA==
X-Gm-Message-State: AKwxytcjd4we61q2DoCjMP86ghRCUVQex9FKCjAOmascfg1IOW6xt5sH uVO9iIiWHJ1Izx9Q1W35lsxee2CtO1FmUKAB36g=
X-Google-Smtp-Source: ACJfBotkt60wancAGii4ndt/1AfiF5wpoU4lXZC+bTa2wuLy/ioHB6A9Xt3RbHTGufnlrMIBqkXA1kNuaXrKV7ieyHA=
X-Received: by with SMTP id n7mr18542065vkc.70.1515647223661; Wed, 10 Jan 2018 21:07:03 -0800 (PST)
MIME-Version: 1.0
Received: by with HTTP; Wed, 10 Jan 2018 21:06:43 -0800 (PST)
In-Reply-To: <>
References: <> <p06240602d67be148b9db@> <> <>
From: Bernard Aboba <>
Date: Wed, 10 Jan 2018 21:06:43 -0800
Message-ID: <>
To: Gunnar Hellström <>
Cc: Randall Gellens <>,
Content-Type: multipart/alternative; boundary="94eb2c14bd865f09d60562791e5a"
Archived-At: <>
Subject: Re: [Slim] Ben Campbell's Yes on draft-ietf-slim-negotiating-human-language-22: (with COMMENT)
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Selection of Language for Internet Media <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 11 Jan 2018 05:07:10 -0000

Which reminds me -- what are the implications of only allowing a single
language to be indicated in an Answer with respect to re-offers?

If multiple languages were indicated in the Answer, wouldn't this make it
easier for an Offer to switch language preferences in a re-offer and
conceivably get an Answer with different preferences?

This is how codec negotiation works today - the Answer can choose the
multiple codecs among those in the Offer, but only the first choice is
expected to be used.

For example, Offer indicates ability to understand Spanish and English,
Answer includes Spanish and English sending ability in that order.

Offerer finds that he/she cannot understand the Answerer very well,
potentially due to the dialect spoken, wishes to switch to English.

This could be indicated via a re-offer with English and Spanish, likely to
be answered with English and Spanish in that order.

Whereas if only a single language were permitted in the Answer, the Offerer
does not know whether the request for a preference change can be accepted
(e.g. if the call would need to be routed to a different endpoint because
the Answerer does not speak English).

On Wed, Jan 10, 2018 at 8:59 PM, Bernard Aboba <>

> Gunnar said:
> ""The result of the negotiation is intended to guide the selection of
> language(s) to use initially and during the session. However, nothing
> prevents the users from varying the use of languages and media by mutual
> agreement after the initial exchange during the call.""
> [BA] This came from Ben Campbell, but other ADs with many years of
> experience in realtime communications have asked questions along similar
> lines.  So it seems that even experienced readers could use some
> clarification.
> The reason for the language selection negotiation is to enable the right
> individuals and resources to be brought into the conversation so as to
> maximize the changes of successful communications. What happens once the
> call is brought up is up to the conversants.
> The precise meaning of the negotiation depends in part on the choice of a
> single language or multiple languages in the Answer.
> If an offer indicates the ability to receive English and French, if an
> Answer can only contain a single language, then an Answer indicating the
> ability to send English would establish that the call is expected to be
> conducted in English. That wouldn't necessarily preclude the use of French,
> but doesn't provide any indication that it could be supported as an
> alternative.
> Whereas if the Answer was allowed to include multiple languages and
> included both English and French, then the Answer would indicate that the
> conversation could use either language with a preference for English over
> French.  That does strike me as potentially valuable in some circumstances
> (e.g. a visitor from Spain with an emergency offering Spanish primary and
> English secondary and being able to get an answer indicating English with
> secondary Spanish support, rather than just English).
> In either case, the conversants can switch languages by mutual agreement.
> On Wed, Jan 10, 2018 at 2:35 PM, Gunnar Hellström <
>> wrote:
>> I saw a question somewhere but lost track of who asked it.
>> It was about if the users are bound to use only the negotiated
>> language(s) in the session.
>> I think a line about that should be inserted, probably best close to the
>> end of the introduction.
>> Proposed text:
>> "The result of the negotiation is intended to guide the selection of
>> language(s) to use initially and during the session. However, nothing
>> prevents the users from varying the use of languages and media by mutual
>> agreement after the initial exchange during the call."
>> Gunnar
>> Den 2018-01-10 kl. 17:12, skrev Randall Gellens:
>>> 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.
>> --
>> -----------------------------------------
>> Gunnar Hellström
>> Omnitor
>> +46 708 204 288