States and transitions
Every state type and transition type a Markov diagram recognises, what to write for each, the absorbing, initial, state class and failed element columns, and transitions a model is allowed to have.
State types
| Node type | Write it as | Under Custom |
|---|---|---|
| State | State, Markov State, System State | Grey circle |
| Initial state | Initial State, Initial, Start State, Operational, Fully Operational, Nominal, Up | Green circle with a heavier border |
| Degraded state | Degraded State, Degraded, Partially Failed, Reduced Capacity, Derated | Amber circle |
| Failed state | Failed State, Failed, System Failed, Unavailable, Down | Red circle |
| Absorbing state | Absorbing State, Absorbing, Terminal State, Trapping State, Permanent Failure | Red circle with a heavy dark red border |
Under IEC 61165:2006 every state is the same plain circle, whatever its type, because that is how the standard's figures draw them. An absorbing state is not marked either.
Matching ignores case, spaces, underscores, hyphens and full stops, so Absorbing_State, absorbing state and AbsorbingState all read as an absorbing state. Wording that matches nothing can be mapped under Node type values on the Data Mapping tab.
Transition types
| Relationship type | Write it as | Under Custom |
|---|---|---|
| Failure transition | Failure, Fails, Failure Rate, Lambda, Degradation, Breakdown | Red arrow |
| Repair transition | Repair, Repairs, Repair Rate, Mu, Restoration, Recovery, Maintenance | Green dashed arrow |
| Transition | Transition, Transitions, Moves To, Goes To, Rate | Grey arrow |
Under IEC 61165:2006 all three are drawn as the same plain arrow; the standard shows a repair as the same arrow pointing the other way. Transition types also help the layout decide which arrows run back towards working order; see Reading a Markov diagram.
Flag columns a register keeps
Many registers write State under Node Type on every row and keep what matters in columns of their own. These bind by name and are carried on each state.
| Column | Binds from | What it does |
|---|---|---|
| Is Absorbing State | Absorbing, Is Absorbing, Absorbing State, Is Absorbing State, Terminal State, Is Terminal, Is Trapping, Trapping State | TRUE, YES, Y, ON or 1 marks a state the system cannot leave. It is checked and drawn as an absorbing state, the same as the Absorbing State type. |
| Is Initial State | Initial, Is Initial, Initial State, Is Initial State, Start State, Is Start State, Is Start | Shown in the Node Inspector and tooltips. More than one state may be marked. It changes neither the drawing nor the checks. |
| State Class | State Class, State Kind, State Category, State Classification | Up, Degraded, Down, or any wording in the state types table. Helps the layout order the states. |
| Failed Element Count | Failed Element Count, Failed Elements, Failed Count, Failed Components, Components Failed, Number Failed | How many elements are down in the state. Helps the layout order the states, more finely than State Class. |
State Class and Failed Element Count are used only when every state has a value, and for State Class a value from that list. A column filled in for some states and not others is ignored for ordering.
A table with no Node Type column binds State Class to Node type instead. Its values then give the states their types: Up is read as an initial state, Degraded as a degraded state and Down as a failed state.
What a model is allowed to have
- Loops. A repair back to an earlier state is expected, and nothing reports a cycle.
- A failure one way and a repair back between the same two states. That is two transitions, not a duplicate.
- A transition from a state back to itself. It is drawn, not reported.
- Several initial states.
- States with no probability, or probabilities that do not add up to 1.
What a model should not have is two transitions between the same two states in the same direction. With the same Transition Type they are drawn as one arrow; with different types both are drawn and reported.