[ticker-dev] Presence specification draft 0.4.1

[Wanicki, Martin]

Hi All,

This is probably my last posting before Christmas, so I'd like to take this
opportunity to wish every one all the best for the season.

The revised presence protocol brings up an issue that may actually improve
the ticker spec, please bear with me while 
I try to explain.

For the purposes of this please consider that the words 'Field' and
'Attribute' to mean the same, its my database background emerging :-)

If missing fields in a notification indicate that a value has not changed it
requires an additional degree of processing in the client
to ensure only existing fields are replaced. Thats fine and fairly trivial
to do, but it leads to something that may be useful in the tickertape
protocol.

In the ticker spec, the "REPLACEMENT" field indicates that the entire
contents of a notification should be replaced, or the original notification
is actually replaced by the new one, whichever way the result is the same
the remaining notification ends up representing whatever notification that
most recently had a replacement id that matched it  To that end it is
conceivable that the replacement function could be extended to perform an
update, updating only existing fields.

So I propose that it may be useful to add an 'UPDATES' field to the
tickertape protocol to not replace a 
notification but to update it with only the changed/supplied fields.

I'm fine to continue without it but I wonder what the ticker community
thinks about this as an idea for a ticker spec extension.

Cheers and all the best

Martin