Transitions are the arrows in a state diagram. Generally, for every arrow you draw in your state diagram, create a transition. Some state diagrams, however, have a lot of arrows pointing to a single state. In that case it might be better to create just one transition that you can reuse in modeling most of the transitions that lead to that state.

Each transition requires a destination state. Select the destination state from the drop-down box. (See Illustration 5 below.)

Illustration 5: Configuring a Transition

Transitions are usually protected by a guard condition. If you drew swimming lanes as suggested in Illustration 2, notice that many of the arrows cross the swimming lanes. Every time you cross a swimming lane you need a guard condition. A guard condition can be a permission, a role, or a workflow expression (described later). Guard conditions ensure that only users with the required permission, role, or other criteria can move the object to the new state.

Most transitions are initiated by a user action. For each transition initiated by a user action, enter the information for the corresponding link that should be displayed to the user in the actions box. The link will only be displayed when the user would be allowed to perform the transition.

Sometimes you need special states and transitions in your workflow diagram that model actions performed in the background, not by any user. In that case you might need to set up transitions that are initiated automatically. Zope will proceed through automatic transitions whenever the guard condition allows it.

Once you have defined all the transitions, go back to your workflow states and define which transitions are allowed to leave those states.