Hi again!
I just had a great discussion with Robot101 in #telepathy. We have
concluded that I should not include this code into Gabble but instead
make a channel plug-in and a channel manager. I don't yet know whether I
should make one channel type like
org.freedesktop.Telepathy.Channel.Type.XPMNServiceConnection (see my
previous e-mail to the list for a suggestion on what this type could
look like) and another channel for every service or just one big channel.
I'm leaning against the former, more modular, approach. The reason for
this is that every XPMN profile is different, and using the generic XPMN
service connection channel type to do the heavy communication lifting
would mean re-using that code in every profile channel, which in turn
would make profile channels much easier to write.
The profile channels' jobs would be to offer a profile-specific API,
maintain a profile-specific state and use the channel type above to
parse the string/XML replies into higher-level data-structures for the
client, and (vice versa) the higher-level data-structures provided by
the client into XMPP XML.
One client could for example say something like (using Java notation):
remoteControlChannel.seek(5125) (where seek is a profile-specific
method) and the channel type would then translate that into an XPMN/XMPP
iq set event and send it to the device.
Perhaps I'm misunderstanding something here. Perhaps I should not be
thinking about channel types as some kind of inheritance. What other
approaches could accomplish the things mentioned above?
Thanks!
Jon Kristensen
On 01/03/2011 03:17 PM, Jon Kristensen wrote:
Hello Telepathy people!
I'm developing an XPMN media server called Pontarius. I'm currently
looking into how XPMN could be integrated with Telepathy. You can read
about Pontarius at http://www.pontarius.org/.
First off, let me clarify some XPMN terms:
*XPMN:* Stands for Extended Personal Media Network and is a
decentralized media network software architecture. It allows extended
media networks to communicate seamlessly and addresses service
discovery (allowing devices to find and identify each other and their
capabilities), security (access control, encryption) and extensibility
(making it easy to extend for future use cases), all while being easy
to set up and use. All-in-all, it's an extremely powerful way to
arrange your media networks.
*Extended media network:* An overlay network consisting (XPMN) devices
from one or more networks, such as home networks. One problem that
XPMN solves is that devices are able to communicate (over for example
Internet) even though they belong to different subnetworks.
*Service:* A specific task or set of tasks that devices may be capable
of fulfilling. One example could be a TV playback and recording service.
*Device:* A logical entity in the extended media network. It does not
have to be a physical device; one physical device can contain multiple
(XPMN) devices. Devices are often bound to a specific action (such as
controlling media playback). A device may be a controller, a service
provider, or both.
*Controller:* A device controlling one or more services. Controllers
can also be service providers. An example of a controller could be a
smartphone application that can act as a remote control for a media
player service, allowing the user to play/pause, change the volume, etc.
*Service provider:* A device providing one or more services. Service
providers can also be controllers.
*Profile:* A profile is an extension on top of the XPMN architecture.
It is a specification that describes a service and includes the
communication protocol used between controllers and service providers.
There can be many implementations of any given profile, and they
should be seamlessly inter-operable.
A XPMN device is basically a connected XMPP account. A directory
service could be using the full Jabber ID
[email protected]/pontarius-directory. XPMN devices
communicate by exchanging general IQ get/set/result messages as well
as a small subset of the pubsub spec (like subscriptions, events and
items requests). Service discovery capabilities also play a part. The
mechanics for this is the same for every profile. See The Status and
Variable Event Mechanism at http://www.pontarius.org/test/0-1-alpha-2/
for a brief (and incomplete) example of what it could look like.
Every XPMN profile has a specialized API for the job that it's doing,
and they all use the above mentioned methods to do their job. One
simple profile could talk to a media player service to do things like
start and stop playback (think remote control), while another profile
can negotiate and download some data over a Jingle and SOCKS5
connection from some kind of transfer service. The external API for
these profiles should be made as simple as possible, and the profile
should hide the "core" XPMN module (from the previous paragraph) from
the third party developer. He should probably only know about the
TpAccount he want to connect with, and the full JID of the service he
wants to talk to. He would most likely be developing a Telepathy client.
I don't really know where the "core" XPMN code and the
profile-specific (remote control, data transfer) code should go, what
it should be (Telepathy channels?) and how they should communicate.
What role could Gabble sidecars play here?
Any ideas, comments or suggestions would be very appreciated!
You can read more in-depth details about XPMN in Dirk Meyer's thesis
at http://elib.suub.uni-bremen.de/diss/docs/00011878.pdf. Also feel
free to ask questions to this mailing-list or to me directly. :-)
Thanks!
Warm regards,
Jon Kristensen
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