Transition
A solid line with an open head, labeled trigger [guard] / effect. Every part is optional. A self-transition is
a compact loop. A transition between a composite state and a vertex inside it is local, drawn to or from the
inside of the border.
diagram state "Transitions"
direction right
[*] --> Waiting
Waiting --> Armed : arm [ready] / log()
Armed --> Armed : tick / count()
Armed --> [*] : done
Syntax
a --> b [: trigger {, trigger} [guard] / effect]
b <-- a
A long label breaks before the effect, then wraps. Pseudostate transitions have limits on which parts they may carry: see Pseudostates and the transition labels section.
Specification
UML 2.5.1. Notation and label syntax: 14.2.4.8 (p. 331). Local and external transitions: 14.2.4.9 (p. 334).