State Machine

A model used in computer science to represent systems and applications.

Blockchains can be modeled as a Trustless state-machine whereby the correct rule of a transition is defined as the state transition function, or STF.

One of the 3 main ways to model a blockchain, as explained in Blockchain Models.

graph LR
y(("$$y$$")) -->|"$$F(x_1,y)$$"| yp(("$$y\prime$$")) -->|"$$F(x_2,y\prime)$$"| ypp(("$$y\prime\prime$$"))

In the above, $y$,$y\prime$, and $y\prime \prime$ are different states. The whole state machine can at any point in time be in either of the states. $F$ is the state transition function and $x_1$ and $x_2$ are the inputs.

In our simple visualizations, the state machine seems to always go forward, but this is not necessarily the case. Normal state machines often involve loops. Even in a blockchain, when a Fork occurs and is eventually discarded, the blockchain state machine might revert back to a previous state.