Actions may include stand-alone expressions, that is expressions without an assignment or if() clause. A stand-alone expression can’t change any attributes but a few expressions have useful side-effects, including use of the runCommand, linkTo, linkFrom, unlinkTo, and unlinkFrom operators.
Often, the output from these operators is of no practical use and this saves the need for adding a user attribute simply to run this type of operator.
The action() function makes it easier to execute standalone code expressions.