Simao,
I see the delivery of CAP alerts (which can be at various levels: authority to authority, authority to citizen but also citizen to citizen) as a multi-faceted issue and not necessarily one tied only to IM in H.323, as this should not exclude H.460.21 message broadcast's functionality. The H.450.7 approach seems part of the solution, even though (correct me if I am mistaken) it would only cover the sinalization that there is an urgent message, not what the message is (basically telling the users to "go and fetch it").
We could actually take one of two approaches with something similar to H.450.7: 1) We can "alert" the user to an urgent message 2) We can deliver the message, rather than simply indicate it's presence Both options require either an extension to H.450.7 or something new entirely, but perhaps similar in structure to H.450.7.
One aspect we need to be aware is that a CAP message can be multilingual and contain a URI to some other content, e.g. a recorded message.
On phones that have a web browser, that could be accommodated by the phone, but for those that merely display text, that certainly presents a problem. Hmmm...
Opening a different can of worms: in the architecture, it is not clear to me who is the gateway for the incoming CAP messages and be able to perform some content translations. For example, beyond the XML to ASN.1 conversion, to do a text-to-speech for audio-only H.323 terminals for delivery of the warning. Or, a distribution node near the end delivery point can perform a de-referencing of an URI inside the CAP message to an A/V content (e.g. for a digital TV distribution).
You're hinting toward what I assumed CAP would actually do: something entirely outside of H.323 itself. I assumed there would be some kind of back-end CAP system that would take the contents and then create audio, video, and/or text, as necessary, and then instruct a special "warning" device that would use H.323 to deliver the message in a human usable form. Carrying CAP within H.323 certainly raises a lot of questions. It's easy to do, but what does a terminal do with it? PSTN gateway devices could not do anything with CAP, so we would still need the network-based warning system to deliver audio messages. (Unless we out a TTS system in every GW, which I think is quite unlikely to happen.) Terminals with display capability are the only devices that can reasonable accommodate reception of CAP messages directly.
I find this development really exciting and seems that if we do a good work here we will get a lot of attention for H.323 also in developing countries as public warning / disaster response is a very hot topic today.
I certainly look forward to some further discussion on this. I'm hesitant to make a submission to this meeting on the topic, but I hope we have some good discussion at this next meeting and come out of the meeting with a plan.
Please do not see this as a discouragement to work on IM, I believe as Paul that this is necessary for H.323's continuation as a
As a? You're out of words? ;-) Paul