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Re: Chronicles

Subject: Re: Chronicles
From: "Shyam Pather [MSFT]"
Date: Thu, 7 Jul 2005 11:05:56 -0700
Newsgroups: microsoft.public.sqlserver.notificationsvcs
I seem to remember you saying you had a copy of my book. If that's so, 
you'll find a detailed discussion of chronicles in Chapter 6. They're also 
covered in the books online and, I think, the stock sample that comes with 
the product.

The gist of it is that you can define arbitrary tables to hold state for 
your application. Chronicles can be associated with event classes or 
subscription classes. Event class chronicles are updated by chronicle rules 
that you define in the ADF as part of the event class. These rules look 
similar to match rules, but rather than generating notifications, they 
simply update whatever state you keep in your chronicle tables, based on the 
latest event data. Subscription chronicles are updated as part of the 
regular match rules.

To handle the duplicate notifications scenario as you've described it, you 
could keep a subscription chronicle that holds information about which 
subscribers were notified about what. You update this table every time you 
generate a notification. In your match rule, you join in this table and use 
it to filter out rows that you don't need to notify about again. There are 
many variations of this e.g. never send duplicates, send a duplicate if a 
certain amount of time has elapsed, send a duplicate if some data value has 
changed beyond a threshold etc. All can be handled via chronicles.

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"andyjax" <[email protected]> wrote in message 
news:[email protected]
> Ok my mind is becoming mush after reading so much.
> I seem to recall that notifications can leverage chronicles to eliminate
> duplicate notifications for an event, such that key information that might 
> be
> triggered is only sent if what was sent before is different.
> I cannot seem to find the reference to this. Any direction would be
> appreciated. 

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