Definition. Synchronization trees [mde-JD4M]

A synchronization tree is a labelled transition system with a distinguished initial state, and the property that for every cocone of transitions \(t_1, t_2\) over a pair of states \(s_1, s_2\), if the transitions of the cocone have the same label then \(s_1 = s_2\) and \(t_1 = t_2\).

These are transition systems without cycles: labelled trees.