Disambiguating Initial State vs Junction Pseudostates in UML State Machines

• Initial State (Initial Pseudostate)

  • Marks where a state machine or composite state begins when first entered.

  • Shown as a filled black circle (●).

  • Has only outgoing transitions, no incoming ones.

  • Example: When an object is created, the machine starts from this point.

• Junction Pseudostate

  • Used to merge or split multiple transitions for better diagram organization.

  • Shown as a small black circle with an outgoing arrow or a small black dot (but connected from multiple transitions).

  • Can have multiple incoming and outgoing transitions with guard conditions to choose the path.

  • Does not represent a starting point, just a decision/merge point.

In short:

• Initial = starting point

• Junction = decision/merge point between transitions

If you want, I can also give you a quick diagram example showing both side by side.
Do you want me to do that?

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