Developing Apama Applications > Developing Apama Applications in Event Modeler > Using Standard Blocks > General analytic blocks > Change Notifier v2.0
Change Notifier v2.0
The Change Notifier block sends out a notification when its input data stream changes by a given amount over a configurable, moving time window. When a sufficiently large positive or negative change has occurred, the output feed will indicate this by setting the changed field to true. The output feed can be configured to automatically reset to its unchanged state a certain time after triggering by setting the reset period parameter.
Parameters
Parameter
Description
period
The maximum age of any sample that is used in the calculations, in seconds. Any samples older than this will be discarded before performing the calculation. Must be greater than zero.
amount
The change amount value, zero to ignore. A notification will be sent if the difference between the oldest value inside the time window and the most recent sample is greater than this amount. Absolute values are used in the calculations.
percentage
The change percentage value, zero to ignore. Absolute values are used as for the amount parameter. 100.0 means to look for a doubling of the input values.
reset period
Following the detection of a big enough change, the output feed will be reset to its un-triggered state after this interval. It is specified in seconds, and is ignored if less than or equal to zero.
At least one of amount and percentage should be different from 0.0, otherwise no notifications will occur.
Operations
Operation
Description
start
Starts checking for changes in the input data feed.
stop
Stops checking for changes.
clear
Discards all stored values.
reset
Resets the changed notification flag.
Input feeds
Feed
Field
Description
data
value
Feed of input values
Output feeds
Feed
Fields
Description
notify
percentage change
The amount of change measured as a percentage.
amount change
The amount of change.
changed
Set true to indicate a sufficiently large change has occurred. Is reset to false by calling operation reset, or after the specified reset period.
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