RE: Re: Displays round the house - architecture...

["Mark Harrison" <Mark.Harrison@xxxxxxx>]

Patrick,

As my old physics teacher said "flash of the blindingly
obvious."

Of course you're right. The decentralised architecture pushing the business
logic to the "output handler" is exactly what's required. That
means that the output handler COULD be a simple device, or could be a
multi-tier thing that stored configuration information in a database as
required.

It's probably as simple as input handlers broadcasting (on a known IP port)
their latest content whenever it changes.

Output handlers then listen to it, and either store, or discard as
appropriate.

Some broadcasts would be treated as triggers. Other as "content store
updates".

The Output handlers could, depending on the device / requirements, be
monolithic, OR multi-tiered, with their configuration stored on a
database.

Cool - all coming together nicely.!

M.



-----Original Message-----
From: PatrickLidstone [mailto:patrickl@xxxxxxx]
Sent: 12 August 2002 16:46
To: ukha_d@xxxxxxx
Subject: [ukha_d] Re: Displays round the house - architecture...


Some random thoughts:
An alternative approach is to let each *display* take the decision 
about what to display locally - transmit message text(s) and triggers 
to all devices. (Note that it is the trigger event, not the trigger 
criteria that is transmitted to a display). I can see a number of 
advantages in this approach:

-  There is no cental controller to fail; it is a distributed 
architecture
-  Triggers can be generated from *any* network connected device, 
possibly including other display units (perhaps with keypads?)
-  Complex conditional logic can be applied (not necessarily excluded
with your original design, depends on what the output server does)
-  Local control and centralised control can be achieved 
simultaneously using the same infrastructure with a minimum of 
additional work.

Configuration information for each display is read from server(s) at 
boot time. This server could also cache recent events so that a 
display shows current information immediately on re-boot.

I think this architecture extends beyond just displays to provide 
(one possible) foundation for an HA network protocol. I could ramble 
on, but I'd wager that a detailed discussion is probably outside the 
interests of the majority of the list. 

Patrick




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