Constructing Flattened Transitions

This algorithm constructs a flattened transition to a state or junction.

Input

1. A state or junction soj₁ representing the source of the transition in the hierarchical state machine.

2. A transition t.

Output

1. A transition that records all actions specified in the source model together with all entry and exit actions implied by the state machine hierarchy.

Procedure

1. If t is an internal transition, then return t.

2. Otherwise

   1. Let A be the actions of t, and let soj₂ be the target of t.

   2. For each i in [1,2]

      1. If soj_i is a state definition sd or is a junction defined in a state definition sd, then

         1. Let sdo_i be Some(sd).

         2. Let L_i be the list of state definitions in the state hierarchy from the top level to sd, including sd, highest first.

      2. Otherwise let sdo_i be None, and let L_i be the empty list.

   3. Let P be the common prefix of L₁ and L₂.

   4. If P is nonempty with last element sd and either sd₁ or sd₂ equals Some(sd), then t represents a self transition, and sd is the outer state definition. Remove sd from P so that we exit and reenter sd.

   5. For each i in [1,2], let L'_i be L_i with the prefix P removed.

   6. Let L''₁ be the reverse of L'₁. Let A₁ be the concatenation of the exit action lists of the elements of L''₁.

   7. Let A₂ be the concatenation of the entry action lists of the elements of L'₂.

   8. Return the external transition whose actions are the concatenation of A₁, A, and A₂, and whose target is soj₂.