/ 25Hong,Shin @ PSWLAB Interpreting P ROMELA models 5/5 chan x = [0] of { bit } ; chan y = [0] of { bit } ; active proctype A() { x!0 unless y?0 } active proctype B() { y!0 unless x?0 } 08:02PROMELA Semantics21 cond: first message in y is 0 effect: none priority : high cond: true effect: x!0 priority : low cond: first message in x is 0 effect: none priority : high cond: true effect: y!0 priority : low x!0y!0 x?0 y?0