Temporal logic of actions

Statements in the temporal logic of actions are of the form ${\displaystyle [A]_{t}}$, where A is an action and t contains a subset of the variables appearing in A. An action is an expression containing primed and non-primed variables, such as ${\displaystyle x+x'*y=y'}$. The meaning of the non-primed variables is the variable's value in this state. The meaning of primed variables is the variable's value in the next state. The above expression means the value of x today, plus the value of x tomorrow times the value of y today, equals the value of y tomorrow.

The meaning of ${\displaystyle [A]_{t}}$ is that either A is valid now, or the variables appearing in t do not change. This allows for stuttering steps, in which none of the program variables change their values.

• Temporal logic
• PlusCal
• TLA+

• Lamport, Leslie (2002). Specifying Systems: The TLA⁺ Language and Tools for Hardware and Software Engineers. Addison-Wesley. ISBN 0-321-14306-X. Retrieved 2007-02-02.
• Leslie Lamport (16 December 1994), Introduction to TLA (PDF), retrieved 2010-09-17

• Official website
• "TLA+ Proof System". INRIA.
• Lamport, Leslie (2014). "Thinking for Programmers". A gentle intro to TLA+ at Build