W3C home > Mailing lists > Public > public-web-intents@w3.org > December 2011

Re: Web Intents - Scenario: TV System (part 6)

From: Greg Billock <gbillock@google.com>
Date: Tue, 6 Dec 2011 15:29:34 -0800
Message-ID: <CAAxVY9fkPZNa=rFO7ThzXGVA1D+KqwbkXCX5Rcd2YsmsNP+UrA@mail.gmail.com>
To: WebIntents <public-web-intents@w3.org>
Thanks for this, timeless. I don't want to speak for you, here, but
I'll put my thoughts inline...

On Tue, Dec 6, 2011 at 2:11 PM, Clarke Stevens <C.Stevens@cablelabs.com> wrote:
> My question on the use case is related to context and state.
> It seems that the primary model for Intents is that (please correct me if
> I'm wrong)
> A (verb) request is made
> A list of (nouns) that can handle (verb) is returned
> The user selects from the list of (nouns) the one to handle the (verb).
> Does the user application know which (noun) handled the (verb)?

In general, no. It is possible in some cases for the return payload to
let the client know the identity of the service. I can't think of a
use case where this is necessary, but it may be desirable in some

> Here's the potential problem:
> If the (verb) is "on" then perhaps several dozen devices in my home will
> respond. In the case of my big TV, I actually want a specific TV in front of
> me to turn on as well as the surround system connected to it. When I turn up
> the volume on my TV, I really want that command to go to the surround
> system, not the TV. When I turn off the system, I may need to know that the
> TV and the surround system are both on in case the power is a toggle switch
> and I don't put them in the wrong state. When I go to a different room in
> the house I want to control a different TV.
> The point is, something has to keep track of context and state. An
> application can certainly do this, but does this work with Intents? The user
> can't be bothered with selecting the (noun) every time the (verb) is
> invoked. Does Intents give enough information to the user application so
> that it can keep track of this? Also, what happens if the user browses to a
> different web page? Is all that information lost?

What I see timeless proposing is that the intelligence of maintaining
this state be resident in the user agent. That is, clever defaulting
policies, with a way for the user to switch assignment, could handle
this. The more complex the use case (and control of
home-network-accessible electronics gear is about the most complex
we've considered), the more complex this defaulting state will be.

> As I've said before, I'm convinced that Intents can be used to discover
> devices, but I still have a lot of questions about whether it is the right
> tool for the other communications tasks.

Right. The alternative to having the UA maintain this state is to use
Web Intents for discovery, and return what amounts to a
message-passing terminal so that the client can then call methods on
some wrapper object which translate into messages to the device. I
think there's discussion of that alternative in other threads (i.e.
[1], so I won't repeat here.

[1] http://lists.w3.org/Archives/Public/public-web-intents/2011Nov/0067.html
Received on Tuesday, 6 December 2011 23:30:02 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:14:45 UTC