W3C home > Mailing lists > Public > public-device-apis@w3.org > February 2013

Re: [discovery-api] Consolidated comments and questions

From: Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr>
Date: Thu, 07 Feb 2013 13:17:38 +0100
Message-ID: <51139B62.7090402@telecom-paristech.fr>
To: public-device-apis@w3.org
A related question: section 6.2 says " */whether the service is 
reporting itself as being either online [...] or offline/*".
In my understanding of the word "offline", the service cannot report 
itself as "offline". That would be a contradiction.
So your definition of "offline" is different than mine.
Can you please clarify this ?

And also, my question about polling boils down to: what is the practical 
difference between "available" and "online" ?

Available is something that UPnP or Bonjour report with various degrees 
of reliability in my practical experience:
- available is reported by UPnP quickly.
- unavailable is reported by UPnP relatively quickly, with some 
occasional long delays.
- available is reported by Bonjour relatively quickly.
- unavailable is reported by Bonjour after a few seconds of delay (3 to 5s).
So this is not so usable, but very clear in terms of implementation: the 
underlying libraries report "service added" or "resolved" for 
availability, and "service removed" for unavailability.

What is "online" ? A response to ping is characteristic of the device, 
not of the service.
Is there anything standard in Bonjour and UPnP that can be used as a 
test of online-ness ?
Should the implementation poll for that ?
Should the online attribute and events not be optional (SHOULD or MAY, 
rather that MUST now) ?
If it is too similar to "available", should it not be removed altogether ?


Le 7/2/13 11:51 , Jean-Claude Dufourd a écrit :
> Le 5/2/13 15:36 , Rich Tibbett a écrit :
>> It will notify you if the number of services available of a type 
>> equal to any of the original requested service types changes in the 
>> network. It's intended as a flag that will allow your web application 
>> to respond to perceived changes in the current network, if it so 
>> wishes to do so (instead of, for example, polling getNetworkServices 
>> every X seconds with a knock-on bad user experience).
> JCD: For online attribute and events, how are you implementing it 
> "underneath" if not by polling ?
> Best regards
> JC

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 - Mob: +33677843843 - Fax: +33145817144
Received on Thursday, 7 February 2013 12:18:06 UTC

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