Junction is a pseudostate (see
Section 20.11, “Pseudostate”) which is used to split an
incoming transition into multiple outgoing transition segments
with different guard conditions. A Junction is also called a
Merge or Static conditional branch. The chosen transition is
that whose guard is true at the time of the transition.
A predefined guard denoted
else may be
defined for at most one outgoing transition. This transition is
enabled if all the guards labeling the other transitions are
According the UML standard, its symbol is a small black
circle. Alternatively, it may be represented by a diamond shape
(in case of "Decision" for Activity diagrams).
ArgoUML only represents a junction on the diagram as a solid
(white by default) diamond, and does not support the black
circle symbol for a junction.