Promela and Model Description
. LTL (continued)
  LTL operators used in Spin expression
  []: always,  <>: eventually,  !: not
  U: until,  V: (dual of U),  &&: and, ||: or,  ->: imply,  <->:equivalence
  ex1: spin –f “[] p”
  ex2: spin –f “p U (q U r)”