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Re: UPnP service implementing an intent

From: Clarke Stevens <C.Stevens@CableLabs.com>
Date: Wed, 23 Nov 2011 11:52:53 -0700
To: Greg Billock <gbillock@google.com>, James Hawkins <jhawkins@chromium.org>
CC: Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr>, "public-web-intents@w3.org" <public-web-intents@w3.org>
Message-ID: <CAF28B56.1531A%c.stevens@cablelabs.com>
I have the opposite problem. I know how UPnP works, but I'm just learning Web Intents.

I am becoming convinced that discovery can work much the same way it does in the Opera/CableLabs API and implementation we submitted to DAP. In this model, the UA does the discovery behind the scenes. When the application wants to do some action, it can register an intent and the UA could recognize and handle it. However, there are a couple of things that I don't yet understand about Web Intents' ability to handle a couple of UPnP (and other protocols) features.

 1.  Persistence  Once interaction with a device is established, there is a presumed ongoing relationship with that device. For example when I start playing a movie, my experience is not complete. I may want to pause the moving (implying that I realize it is playing and I want to pause it). I may want to maintain some sort of counter in my UI to indicate how much of the movie is remaining. I may want to transfer the playback of the movie to a different television. I would imagine I can keep track of such things as a feature of the UA or in my application. Is this the expected solution?
 2.  Events  There are numerous cases in which a device handling an intent must initiate communication back to the device that requested the intent WITHOUT any corresponding request. Is this possible with intents? If so, what is the expected way to do this?


From: Greg Billock <gbillock@google.com<mailto:gbillock@google.com>>
Date: Wed, 23 Nov 2011 11:17:16 -0700
To: James Hawkins <jhawkins@chromium.org<mailto:jhawkins@chromium.org>>
Cc: Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr<mailto:jean-claude.dufourd@telecom-paristech.fr>>, "public-web-intents@w3.org<mailto:public-web-intents@w3.org>" <public-web-intents@w3.org<mailto:public-web-intents@w3.org>>
Subject: Re: UPnP service implementing an intent

Web Intents as an API is a way for clients to request particular functions of generic services and receive replies (or, viewed the other way, for services to receive requests from arbitrary clients and provide replies).

There's a mechanism in our proposal for web pages to indicate to the browser that they can service intents, but that is not the limit of what entities could participate in the ecosystem. It is equally possible for the browser to provide built-in services or for those services to be registered by and handled by OS-resident applications.

I don't have a firm grasp on the scope of the use cases for home networking discovery, but the intents API would be sufficient to, for example, send a request to a particular piece of attached equipment and get a response.

Example use case:
A web app wanted to play a song; it could prepare an intent payload with the song and issue a "play" intent.

navigator.startActivity(new Intent("play", "audio/mp3", song));

The browser consults its UPNP directory (I know nothing about how that works, but presumably the browser could keep track of registered attached devices and their capabilities.) It finds two devices that know how to play MP3s and presents the user with a picker. The user chooses to play the song on one of them, and the song plays.

I'm sure this simple example doesn't capture the full scope of the problem. Perhaps it shows why there is hope the problems are related, though?

On Wed, Nov 23, 2011 at 9:03 AM, James Hawkins <jhawkins@chromium.org<mailto:jhawkins@chromium.org>> wrote:
Can't the UA receive the broadcast of the UPnP service and add it to the intent registry?  In general our model has the UA being the broker for platform-level interactions with intents.


On Wed, Nov 23, 2011 at 7:38 AM, Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr<mailto:jean-claude.dufourd@telecom-paristech.fr>> wrote:
Dear all,

In the Home Network TF of Web and TV IG, we discussed discovery of services, including the discovery of those services offered through existing protocols such as UPnP.
I heard at the TPAC that web intents are the way to satisfy the HNTF requirements on discovery.
>From reading the emails on this list, I do not see how it is possible to wrap UPnP services as intents.
It seems a mediator or proxy would be needed, receiving the initial broadcast of the UPnP service announcing itself, translating that to an intent registration and sending it to the intents broker.
If so, then no, web intents do not satisfy the HNTF requirements on discovery, or at least, there is a significant missing part.
Best regards

JC Dufourd
Directeur d'Etudes/Professor
Groupe Multimedia/Multimedia Group
Traitement du Signal et Images/Signal and Image Processing
Telecom ParisTech, 37-39 rue Dareau, 75014 Paris, France
Tel: +33145817733<tel:%2B33145817733> - Mob: +33677843843<tel:%2B33677843843> - Fax: +33145817144<tel:%2B33145817144>
Received on Wednesday, 23 November 2011 18:53:28 UTC

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