Syntax and Semantics

Syntax

• Propositional logic
• Modality
  • □ - necessarily, e.g., □ logic_is_good
  • ◊ - possibly, e.g., ◊ i_am_confused

Semantics

• Semantics of propositional logic as usual
• Reachability relation between propositional interpretations
  • □ X iff X in all reachable interpretations
  • ◊ X iff X in some reachable interpretation