The Logic of Actions

Values, variables and state.

• Collection Val of values.
  • Algorithms manipulate data.
  • Numbers, strings, sets.
• Infinite set Var of variable names.
  • Algorithms assign values to variables.
• A state assigns values to variables.
  • $s$ in St = Var -> Val.
  • $s$[[$x$]] := $s(x)$.
  • [[$x$]] in St -> Val.
  • Semantic meaning [[$x$]] of syntactic object $x$.