Activity Chart Checks : (C4137) Elements that flow from/to router without a matching flow in ancestor chart

(C4137) Elements that flow from/to router without a matching flow in ancestor chart

Error In:
Completeness
Description:
There are elements that flow from or to the router without matching flow-lines higher in the hierarchy.
Note that this test avoids warnings for empty information-flows. (This behavior is consistent with Check-Model tests C4058 and C4059.)
Example:
Consider the example in the following figure - Tested Activity-chart: AC2_3
(C4137) Elements that flow from/to router without a matching flow in ancestor chart:

Y flows from ROUTER_1 to AC2_3

W flows from AC2_3 to ROUTER_1

Erroneous Elements:
Events, conditions, data-items, information-flows, and fields