A choice rule must not return implicitly by reaching the end of the rule. Form 11 is the invocation of an update semantic operation. Similarly, form 12 is the invocation of a parameterized update operation. The parameter value, which must be of the operation's parameter type, is supplied to the invocation of the operation. Form 13 is a semantic choice.
Execution continues with the first action of the alternative whose label matches the returned value.
If none of the alternative labels matches the value, the otherwise alternative is taken. Following execution of the last action in the chosen alternative, execution continues following the choice. Similarly, form 14 is a parameterized semantic choice. The parameter value, which must be of the operation's parameter type, is provided to the invocation of the choice operation. Each alternative label in a semantic choice must be a value of the result type of the choice operation.