In activity diagrams, call operations are actions that you can use to invoke operations in a model. The referenced operation defines a type of behavior, such as a transformation or a query, that the target object can execute.
The values specified in the input pin of the call operation define how the referenced behavior executes. These input values must be compatible with the operation parameters and the class that owns the operation.
Each call operation has a unique name that is synchronized with the operation that is referenced.
As the following figure illustrates, a call operation is displayed as a rectangle with rounded corners that contains the name of the operation. An input pin, represented by a small square that contains an open arrowhead, is attached to the left side of the call operation.