# DES Consistency

A DES is consistent if it meets the following criteria:

1. The name of the DES does not contain invalid characters.
2. Each state in the DES has a unique name within the DES statespace.
3. The DES must have one and only one initial state.
4. The DES must have at least one marked state.
5. The DES must have at least one event.
6. Each event in DES has a unique name (label) within the DES event space.
7. The DES must be deterministic. This means a single initial state and no two transitions leaving the same state with the same event label.
8. The DES must be reachable. This means that there must be a path from the initial state to every state in the DES.
9. The DES must have at least one transition.
10. If the DES is of type Interface, each event in DES must be either request, answer or low data.

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