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From Monotonic Transition Systems to Monotonic Games. Parosh Aziz Abdulla Uppsala University. Outline. Model Checking Infinite-State Systems Methodology: Monotonicity Well Quasi-Orderings Models Petri Nets Lossy Channel Systems Timed Petri Nets Extension to Games.
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From Monotonic Transition Systems to Monotonic Games Parosh Aziz Abdulla Uppsala University
Outline • Model Checking • Infinite-State Systems • Methodology: • Monotonicity • Well Quasi-Orderings • Models • Petri Nets • Lossy Channel Systems • Timed Petri Nets • Extension to Games
Model Checking Tsatf? transition system specification
Transition System Model Checking Tsatf? transition system specification
Transition System Reachability Init Fin InitreachesFin?
Transition Systems Reachability Init Saftey Properties = Reachability Fin InitreachesFin?
Forward Reachability Analysis Post Forward Reachability Analysis = computing Post Init Fin
Backward Reachability Analysis Pre Backward Reachability Analysis = computing Pre Init Fin
Forward Reachability Analysis Init Fin Backward Reachability Analysis Init Fin
Infinite-State Systems 1. Unbounded Data Structures • stacks • queues • clocks • counters, etc. 2. Unbounded Control Structures • Parameterized Systems • Dynamic Systems
Backward Reachability Analysis Init Fin infinite
Backward Reachability Analysis Init Fin infinite effective symbolic representation
Transitions t Firing t
Transitions t t is disabled
Mutual Exclusion W R=1? R:=1 R:=0 C
Mutual Exclusion W R=1? R:=1 R:=0 C R=1? R=1? R=1? R:=1 R:=1 R:=1 R:=0 R:=0 R:=0
Mutual Exclusion R=1? R=1? R=1? R:=1 R:=1 R:=1 R:=0 R:=0 R:=0
Mutual Exclusion R=1? R=1? R=1? R:=1 R:=1 R:=1 R:=0 R:=0 R:=0 • Initial states: • R=1 • All processes in Infinitely many
Mutual Exclusion R=1? R=1? R=1? R:=1 R:=1 R:=1 R:=0 R:=0 R:=0 • Initial states: • R=1 • All processes in Infinitely many Bad states: Two or more processes in
Mutual Exclusion R=1? R=1? R=1? R:=1 R:=1 R:=1 R:=0 R:=0 R:=0 R=1 C W
R=1 C W Mutual Exclusion Set of initial states : infinite
R=1 C W Mutual Exclusion
R=1 C W Mutual Exclusion R=1 C W
Mutual Exclusion R=1 C W
R=1 C W Mutual Exclusion R=1 C W
Safety Properties • mutual exclusion: • #tokens in critical section > 1 critical section
Safety Properties • mutual exclusion: • #tokens in critical section > 1 Ideal = Upward closed set of markings critical section
Safety Properties • mutual exclusion: • #tokens in critical section > 1 Ideal = Upward closed set of markings critical section safety = reachability of ideals
Petri Nets • Concurrent systems • Infinite-state: symbolic representation • Monotonic behaviour • Safety properties: reachability of ideals
Petri Nets • Concurrent systems • Infinite-state: symbolic representation • Monotonic behaviour • Safety properties: reachability of ideals
Monotonicity ideals closed under computing Pre
Monotonicity ideals closed under computing Pre I
Monotonicity ideals closed under computing Pre I
Monotonicity ideals closed under computing Pre I
Monotonicity ideals closed under computing Pre Pre(I) I