Software Architect's Handbook

Fork/join nodes

When you want to model a single flow forking into two or more concurrent flows, you use a fork node. When you want to combine two or more concurrent flows back into a single outgoing flow, you use a join node. The following diagram illustrates a flow that has a fork and join node:

Both fork and join nodes are graphically represented with either a horizontal or vertical bar. The orientation of the bar is dependent on whether the flow is going from top to bottom or left to right. When fork and join nodes are used together, they are sometimes referred to as synchronization.