Notation for choices of symbols
A choice among several alternatives is indicated by branches in the tracks, as in the example below where you have several options for specifying a method’s characteristics.
SimpleAction
The following program fragments illustrate how to use this rule.
action onload()
{
}
action onunload()
{
}
action ondie()
{
}
action myAction()
{
}
In the preceding example, you had to choose one of the four alternatives. Sometimes the choices are optional and you can choose one of the options or none. In the following diagram, you can optionally include a SequenceInitializer.
SequenceDeclaration
This is indicated by a straight-through track with the optional construct below it. When there are multiple options, they are shown "stacked", as shown in the next diagram.
Digits1
This means you must choose from one of the digits 0 through 9. For the sake of brevity, the notation .. is often used to indicate a sequence of consecutive characters from which you can choose one. Thus the following diagram means exactly the same thing as the longer form of Digits shown in the previous diagram.
Digits2
