Statechart Checks : (C15002) Either ‘send’ or ‘receive’ are operated on non-message elements

(C15002) Either ‘send’ or ‘receive’ are operated on non-message elements

There are Data-Items, which are used with the operators send (sn!()) or receive (rc!()), without being defined as Messages in their Design-Attributes.
Error In:
Design
Erroneous Elements:
Data-Items