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Versions: 00 01                                                         
SLIM                                                           N. Rooney
Internet-Draft                                                      GSMA
Expires: September 22, 2016                               March 21, 2016

                             SLIM Use Cases


   Use cases for selection of language for internet media.

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1.  Introduction

   The SLIM working group is developing standards for language selection
   for non-real-time and real-time communications.  There are a number
   of relevant use cases which could benefit from this functionality
   including emergency service real-time communications and customer
   service.  This document details the use cases for SLIM and gives some
   indication of necessary requirements.  For each use case a 'Solution'
   is provided, indicating the implementability of the use case based on

2.  Use Cases

   Use cases are listed below:

2.1.  Single two-way language

   The simplest use case.  One language and modality both ways in media
   described in SDP [RFC4566] as audio or video or text.
   Straightforward.  Works for spoken, written and signed languages.  An
   example is when a user makes a voice call and the preferred language
   of that user is specified in SDP, allowing the answerer to make
   decisions based on that specification.

   o  Solution: Possible

2.2.  Alternatives in the same modality

   Two or more language alternatives in the same modality.  Two or more
   languages both ways in media described in SDP as audio or video or
   text, but only in one modality.  Straightforward.  Works for spoken,
   written and signed languages.  The answering part selects.  There is
   a relative preference expressed by the order, and the answering part
   can try to fulfill that in the best way.  An example is a user who
   makes a voice call and prefers French first and German as their
   second language, and the answerer selects to speak German as no
   French speaking abilites are available.

   Solution: Possible

2.3.  Fairly equal alternatives in different modalities.

   Two or more modality alternatives.  Two or more languages in
   different modalities both ways in media described in SDP as audio or
   video or text.  An example is a hearing person also competent in sign
   language declares both spoken and sign language competence in audio
   and video.  This is fairly straightforward, as long as there is no
   strong difference in preference for these alternatives.  The

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   indication of sign language competence is needed to avoid invoking
   relay services in calls with deaf sign language users only indicating
   sign language.

   Solution: Possible

2.4.  Last resort indication

   One language in the different modalities.  Allows the user to
   indicate one last resort language when no other is available.  For
   example, a hearing user has text capability but want to use that as
   last resort.  (With current hunintlang specification, there is no way
   to describe preference level between modalities and no way to
   describe absolute preference.)

   Solution: An answering service will have no guidance to which is the
   preferred modality and may select to use the modality that is the
   callers last resort even if the preferred alternative is available.

   Another practical case can be a sign language user with a small
   mobile terminal that has some inconvenient means for texting, but
   sign language will be strongly preferred.  In order to not miss any
   calls, the indication of text as last resort would be desirable.
   Possible solution: coding of an absolute preference: hi, med, lo
   together with the tag.

   Solution: Need for absolute preference indication.

2.5.  Directional capabilities in different modalities

   Two or more language alternatives in the different modalities.  For
   example, a hard-of-hearing user strongly prefers to talk and get text
   back.  Getting spoken language input is appreciated.  This can be
   indicated by spoken language two-ways in audio, and reception of
   language in text.  (There is no current solution that says that the
   text path is important.  The answering part may see it as an

   Solution: Need for preference indication per modality

2.5.1.  Fail gracefully?

   There currently are methods to indicate that the call shall fail if a
   language is not met, but that may be too drastic for some users
   including the one in the above scenario (2.5).  It may be important
   to be able to connect and just say something, or use residual hearing
   to get something back when the voice is familiar.

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   Possible solution: coding of an absolute preference together with the
   tag could solve this case if used together with the directional
   indications.  For example:

   "preference: hi, med, lo"

   Another solution would be to indicate required grouping of media,
   however this raises the complexity level.

2.6.  Combination of modalities

   Similar to Section 2.5, two or more language alternatives in the
   different modalities.  A deaf-blind person may have highest
   preference for signing to the answerer and then receiving text in
   return.  This requires the indication of sign language output in
   video and text reception in text, using the current directional
   attributes.  An answering part may seek suitable modalities for each
   direction and find the only possible combination.

   Solution: Need for preference indication per modality

2.7.  Person with speech disabilities who prefer speech-to-speech

   One specific language for one specific modality with a speech-speech
   engine.  A person who speaks in a way that is hard to understand, may
   be used to have support of a speech-to-speech relay service that adds
   clear speech when needed for the understanding.  Typically, only
   calls with close friends and family might be possible without the
   relay service.

   This user would indicate preference for receiving spoken language in
   audio.  Text output can be indicated but this user might want to use
   that as last resort.  (There is no current coding for vague or
   unarticulated speech or other needs for a speech-to-speech service.)

   A possibility could be to indicate no preference for spoken language
   out, a coding of proposed assisting service and an indication of text
   output on a low absolute level.

   Solution: Need of service indication, and absolute level of
   preference indication.

2.8.  Person with speech disabilities who prefer to type and hear

   Two or more language alternatives for multiple modalities.  A person
   who speaks in a way that may be hard to understand, may be used to
   using text for output and listen to spoken language for input.  This

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   user would indicate preference for receiving spoken language in
   audio.  Text output modality can be indicated.

   If the answering part has text and audio capabilities, there is a
   match.  If only voice, there is a need to invoke a text relay

   Solution: Need of service indication, and absolute level of
   preference indication.

2.9.  All Possibilities

   Mutiple languages and multiple modalities.  For example: a tele-sales
   center calls out and wants to offer all kinds of possibilities so
   that the answering party can select.  A tele-sales center has
   competence in multiple spoken languages and can invoke relay services
   rapidly if needed.  So, it indicates in the call setup competence in
   a number of spoken languages in audio, a number of sign languages in
   video and a number of written languages in text.  This would allow,
   as a further example, a deaf-blind person who prefers to sign out and
   get text back answers with only these capabilities.  The center can
   detect that and act accordingly, this could work in the following

   o  Solution Alternative 1: The center calls without SDP.  A deafblind
      user includes its SDP offer and the center sees what is needed to
      fulfill the call.

   o  Solution Alternative 2: The center calls out with only the spoken
      language capabilities indicated that the caller can handle.

   The deaf-blind answering person, or terminal or service provider
   detects the difference compared to the capabilities of the answering
   party, and adds a suitable relay service.  (This does not use all the
   offerings of the callers competence to pull in extra services, but is
   maybe a more realistic case for what usually happens in practice. )

   Solution: Possible in the same way as cases 1.8.

3.  Final Comments

   The use cases identified here try to cover all cases of when users
   wish to make text, voice or video communication using the language of
   set of languages in which they are able to speak, write or sign and
   for which the receivers are also able to communicate.  Some of these
   use cases go even further to allow give some users the ability to
   select multiple and different languages based on their abilities and

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   To fulfill all the use cases the currently specified directionality
   will be needed, as well as an indication of absolute preference.  An
   indication of suitable service and its spoken language is needed for
   the speech-to-speech case, but can be useful for other cases as well.
   There is no clear need for explicit grouping of modalities seem to be

   Subsequent work in the Selection of Language for Internet Media
   Working Group (SLIM: https://datatracker.ietf.org/wg/slim/charter/)
   will work on Internet Drafts to support these use cases.

4.  Security Considerations

   Indications of user preferred language may give indications as to
   their nationality, background and abilities.  It may also give
   indication to any possible disabilities and some existing and ongoing
   health issues.

5.  IANA Considerations

   This document has no IANA actions.

6.  Informative References

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <http://www.rfc-editor.org/info/rfc4566>.

Appendix A.  Acknowledgments

   Gunnar Hellstrom's experience and knowledge in this area provided a
   great deal of these use cases.  Thanks also goes to Randall Gellens
   and Brian Rosen.

Author's Address

   Natasha Rooney

   Email: nrooney@gsma.com
   URI:   https://gsma.com

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