RE: x-ap / xap wassit all about?

["John B" <home-automation@xxxxxxx>]

> The last time I was on this list was a year or so ago and x-ap or xap
was in
> its infancy ...
>
> Just out of curiosity (at the moment) would you be able to tell me
what *it*
> is ... and what are the uses for *it* .. and the benefits if any..

Well, I can certainly tell you a bit about xPL, but I guess much of this
will apply to xAP as well, as the original design goals are much the same.

The usual explanation goes something like:
"xPL is an open protocol intended to permit the control and monitoring
of home automation devices throughout the home."

Basically, it is a standard protocol, allowing all kinds of devices
(ranging from PC apps to embedded hardware) to "speak" the same
language.

There are predefined schemas, e.g. for audio, X10, digital/analogue
control, infra-red etc. This allows devices of the same class to be
controlled using the same message.
For example, if you send a stop message to an audio player, it doesn't
matter whether it's Winamp, Real Player, a SliMP3, a SqueezeBox, a Rio...
they will all respond to exactly the same message in the same way.
There are usually extensions to the common schemas to allow for
device-specific functionality, but common features such as play, stop,
next, prev etc. are the same across the board.

Benefits:

To try and explain the benefits of an xPL-enabled home, I'll start with an
example:

Consider three pieces of hardware:
A Meteor caller ID unit,
An X10 CM12U computer interface,
A SliMP3  Ethernet music player.

Suppose you want to have caller ID displayed on the SliMP3, and you want to
use a button on the SliMP3 remote control to turn on a light using X10.

In the days before xPL, here's how you'd do it:

You'd need an application to talk to the Meteor that could extract the CID
info, then connect to the SliMP3 server's command-line interface to display
the message.
This would almost certainly involve writing a custom app.

Next, you'd need to write a plug-in for the SliMP3 that could talk to your
CM12 so that button presses on the SliMP3 could send out X10 commands.
But what if you were already using the CM12 with Homeseer? Then you'd need
to interface the SliMP3 with Homeseer instead.

As you add more and more devices, the number of custom links that you need
to build up between them increases.

With the xPL approach, you need the following:
- An xPL connector for the Meteor
- An xPL connector for the CM12
- A central controller to handle processing logic

Note that the SliMP3 supports xPL out-of-the-box, so you don't need any
additional software to use it in an xPL environment.

As soon as a device becomes xPL enabled (either through native support, or
through use of a connector/gateway application) it becomes available to
every other xPL-enabled device in your home.

Add in a central controller to perform intelligent decision-making (e.g.
xPLHal) and you have the basis for a very powerful home automation system
that is unbelievably easy to expand, and offers a degree of flexibility
that was previously unheard of without needing to do a lot of custom
programming/scripting.

There's also the plug-n-play side to xPL:
There is a complete mechanism for device discovery and configuration,
meaning you can add a new device to your network and have it up and running
in a few seconds.

If you want to know more about xPL, see:

http://www.xplproject.org.uk/
http://www.xplhal.com/
http://groups.yahoo.com/group/ukha_xpl/

Regards,

John


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