CallOperationAction of SysML

[vikas]

Hi,
I'm a little confused about the "call operation action" of activity
diagram of SysML. Below is what i understand about the call operation
action and what i don't understand. Please correct me if necessary and
answer my question.

Call operation action is used to invoke a operation (or function)
defined in a "block definition diagram" or a pre-defined operation in
sysml. Input pins (attached to callOperationAction node) can be used
to specify the arguments (parameters) passed to the operation. The
output pins represent the results obtained from the operation. There
can be any number of input and output pins attached to the call
operaton action node.
I don't understand the use of the "target" input pin which needs to be
present to make a valid call opertaion action. Please somebody explain
what is the purpose of having the target input pin and what does it
signify?

Thanks in advance,
Vikas Patel

[Tim Weilkiens]

The call operation needs a target for the call, i.e. the object that
receives
the call. The target pin specifies that object.

The calloperationaction only specifies that an operation X must be
called, but
not the object itself.

Tim