Activity Chart Checks : (C4071) Elements affected by an activity but are neither used internally nor output

(C4071) Elements affected by an activity but are neither used internally nor output

Error In:
Completeness
Description:
There are elements that are affected (modified or generated) in the mini-spec of an activity, but are neither used in this mini-spec nor as output of the activity.
Example:
In the figure, activity INST2 has the following mini-spec:
C/X=4;Y=2
X is not shown as an output on the chart and is not used internally within the mini-spec; however, it is affected by INST2.
Erroneous Elements:
Events, conditions, and data-items