UML14 — How does one indicate the target object for a CallState

How does one indicate the target object for a CallState (i.e. the actual
object that executes the stated action/method)? If the target action takes
no parameters then it may be possible to say that the target object is just
the object flowing into the CallState. But what if it does take parameters?
(e.g. the Person.Drive(to: Place) example in Fig. 3-88). That would require
more than one object to be flowing into the CallState and leads to an
ambiguity about which constitutes the target and which the parameter.

P.S. The actual object may be passed around by the activity diagram, so it
is not possible to show it statically on a swimlane (even if that is the
recommended way)

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