[Dev] Comments on Observable Queries Re: Dev digest, Vol 1 #186 - 1 msg

Andrew Francis andrewfr_ice at yahoo.com
Sat Sep 27 13:06:15 PDT 2003


>Brian Skinner is maintaining a Help Us! page on the
>Chandler Wiki. This page is for small,
self->contained, projects with clear deliverables 
>which would help OSAF enormously. 
>http://wiki.osafoundation.org/bin/view/Main/HelpUs

I read the "Observable Queries Prototype" section
and the beginning of the "Observable Queries" pages. 
I have comments on the following scenario.

BS>"Question: Let's say the user has two views, a 
BS>Day View that shows Thursday, and a Week View 
BS>that shows the whole week. Suppose the user, in 
BS>Week View, drags a "Lunch" event from the Wednesday
BS>column and drops it on the Thursday column. How 
BS>does the separate Day View find out that it needs
BS>to display the "Lunch" event?"

BS>Answer: 
BS>observer/observable: In scenario 1 we used a
BS>simple "observer/observable" mechanism to register
BS>interest in individual objects, but that won't 
BS>work now. In scenario 2, the Day View has never
BS>displayed the "Lunch" event before, and has never
BS>registered as an observer, so it is never notified
BS>of the edit. 

I sketched out your example and I don't see why an
observer/observable model could not handle the 
aforementioned scenario. In the observer/observable
model, I would suspect that the Week and Day View 
would be registered to declare their interest in
changes to the Calendar model's state.

When an end-user drags a lunch event from Wednesday 
to Thursday, this translates into the Calendar being
updated and some type of update notification (event)
being  generated and sent to the observers. The 
update notification could either contain information
about the state change, or can be a signal for the
observers to fetch the appropriate Calendar state
information. 

In the case of the Day viewer, the viewer would 
respond by grabbing information about Thursday events,

(since that is what it is currently viewing) and 
would consequently display the new Lunch event. If
the viewer was smarter, it may check the Calendar
against its internal representation to see if things
have indeed changed.......

Cheers,
Andrew











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