Subject: RE: [Widex] Review of Requirements document

From: <[email-masked]>
Date: Thu, 7 Sep 2006 18:48:56 +0300

Hi Lisa,

>-----Original Message-----
>From: ext Lisa Dusseault [mailto:[email-masked]] 
>Sent: 21 July, 2006 22:29
>To: [email-masked]
>Subject: [Widex] Review of Requirements document
>
>
>This review comes from me as an individual.  These are 
>questions and suggestions for improving the document (not 
>requirements from your advising AD), and it may well be that I 
>don't understand the problem space well enough yet.
>
>4.  Scenarios
>
>I am not sure why the NAT traversal and IPv4/IPv6 stuff is in 
>this document in so much detail.  Does it require this much 
>explanation and diagrams?  What requirements follow from these 
>scenarios?

The relation might not be so obvious but, as Widex will define both a
framework and a message exchange used for synchronization (e.g. WOs),
implementers needs to be aware of the network environment challenges
when they will choose the service discovery and session setup mechanism
and the transport protocol that is most appropriate for their particular
target environment. We might have gone too deep into details in this
document and a better place for those should have been the framework
document but they are quite important to understand the problem.

>
>To a reader like me, a scenario that described an example use 
>case justifying the "multiple modes of interaction" would be useful.

Would it be enough if we point the reader instead to the W3C's
Multimodal Architecture which is one possible customer of the Widex
framework?

>
>I think your scenarios are designed for a reader that 
>understands the problem that's being solved but may not 
>understand the networking challenges, whereas I'm a reader who 
>understands the networking challenges more than I understand 
>the problem being solved :)
>
>5.  Requirements
>
>5.1:
>"   o  The framework MUST be modular, e.g. multiple session setup
>       mechanisms may be used."
>
>Flexibility is good; interoperability is even better.  How 
>about adding something like: "There must be ONE 
>mandatory-to-implement session setup mechanism" (you might 
>also add desired characteristics for the mandatory mech.)

The Widex framework can be used in different environments and those can
have characteristics that differentiate them quite a lot and these
characteristics were taken into account by the developers of the service
discovery and session setup protocols. For example, in an unmanaged
network like those typically found in home networks, an implementer may
choose between Rendezvous/Bonjour and UPnP. In other environments, where
SIP infrastructure is available, implementers can use it. Other
alternatives include SLP or SRV records or it might be possible that in
some close environments there is no need for service discovery and
session setup at all if you have means to manually input the URL of the
server in the client.

It would be great if a mandatory mechanism will be defined but it seems
that we don't have any mechanisms that is universally applicable. For
this reason, in order to help interoperability and to provide a somehow
unified experience regardless of what is the actual service discovery
and session setup mechanism, the framework has some requirements on what
the mechanism must and should negotiate (they are listed in the
framework draft).

>
>5.2:
>"   o  The service discovery mechanism MUST be able to discover both
>       Widex Renderers and Widex Servers."
>
>At a minimum, there are Security Considerations implications 
>from this, particularly w.r.t. privacy of renderers.  I would 
>like to understand better the reasoning behind the requirement 
>for discoverability of Widex renderers.

A TV set or a smart screen can play very well the role of Widex renderer
and it might be useful if you could use this as a secondary display. Of
course, privacy of the renderers is very important and implementers
should balance what capabilities should be revealed and which should be
kept private. For example, somebody can choose not to reveal anything
about the renderer besides that it is a Widex renderer but that will
have quite negative impact as the server will not be able to provide the
UI that best suits the renderer capabilities, instead providing the
default UI.

Privacy concerns are valid also for the Widex servers which might host
sensitive applications and you want to allow only specific
users/renderers to interact with. Fortunately, these issues were taken
into account by the designers of service discovery and session setup
mechanisms. 

>
>5.3:
>"   o  The WOs MUST contain only information having remote scope."
>
>I just don't understand this requirement.

The meaning of WOs was defined in section 3.3. and specifically refers
to the WOs.Event. Do you think that we need to be more specific about
which WOs this requirement is about? We need to think that while
developing the framework document we detected that we need more WOs than
initially envisioned in this document (e.g. WO.Selector) and the
requirement should cover also those ones.

>
>5.3:
>"   o  The WOs MAY support multiple modes of interaction, and it is the
>       responsibility of the application to synchronise modalities and
>       not that of the Widex protocol."
>
>I believe this implies that multiple modes would indicate 
>multiple Widex protocol sessions. Is that correct?  It might 
>be good to state the implication.

Yes, this implication in correct.

>Thanks,
>Lisa

Thanks,
Vlad

_______________________________________________
Widex mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/widex

---

From: Dean Willis <[email-masked]>
Date: Mon, 18 Sep 2006 14:13:09 -0500

It seems to me that the commentary from Lisa indicates a few things  
that should be touched up before requesting Apps-area expert review  
on the document, which I would like to do either before or in  
conjunction with working-group last call.

With a document of this sort and the small community that we have  
working on it, I think it is important to get some external review so  
that we can discover whether the level of exposition is adequate for   
a new reader.

What do you folks think of revving this document fairly quickly to  
accommodate the suggestions below, then starting area and working  
group final reviews?

--
Dean Willis, as chair

---

From: Lisa Dusseault <[email-masked]>
Date: Tue, 19 Sep 2006 16:17:03 -0700

Discussion continued below inline...

> document but they are quite important to understand the problem.

I'm still concerned about the risk of describing NATs, or suggested  
solutions to the problems NATs post, in a way that's incompatible  
with the many other documents the IETF has produced on the topic.  It  
feels odd to type that; I'm generally in favour of explanatory text  
to help implementors!  I guess I'm not suggesting simply taking out  
the text, unless you really can refer to some BEHAVE or transport  
area document.  At some point it would need to be tied, as you  
suggest, to helping implementors choose the appropriate WIDEX options  
for their environment.  I would support moving this to the framework  
document.

> Multimodal Architecture which is one possible customer of the Widex

Probably yes

> the mechanism must and should negotiate (they are listed in the

I was a little confused here by what a "session setup mechanism" is.   
Here's what I was thinking: TCP is expected to work all over the  
Internet, and there's one way to create a session in TCP.  If you  
want a fancier kind of setting, BEEP or XMPP could work anywhere TCP  
works, and each of those have one way of creating a session.  So I  
was thinking WIDEX would require support for one of those.

But if you're indeed talking about service discovery, then I agree  
there's not one standardized mechanism that's guaranteed to work  
everywhere and be useful for each case.  Not every WIDEX server will  
be able to create SRV records, for example.  Still, if service  
discovery is very important for WIDEX (it isn't in email and  
calendaring where users type in their server addresses) then there'll  
need to be a lot of thought about whether the existing mechanisms are  
sufficient or whether WIDEX needs to "raise the bar" in this area by  
demanding (or specifying ) more.

> UI that best suits the renderer capabilities, instead providing the

You might want to explain the use case that illustrates or motivates  
the requirement, in the requirements doc.  (I don't think exhaustive  
use-casing is very successful in IETF but in this case I just didn't  
get it without an example)

> requirement should cover also those ones.

I read "WOs" as short for "Widex Objects".  I don't agree it implies  
Event as is.  There were other problem words -- "having scope" and  
which end "remote" is.

Would this be correct?  "  o  The Widex Objects MUST contain only  
information meaningful in context of the renderer."