1. TIOA-to-UPPAAL Translator & Front-End Integration
Radu Grosu, Scott A. Smolka, Wenkai Tan
Stony Brook University
VeroModo Workshop, MIT, May 18, 2006

2. The TIOA-to-Uppaal Translator
Uses Front-End to translate TIOA specs into input language of UPPAAL model checker for Timed Automata.
Only UPPAAL-compliant subset of TIOA language is translatable.

3. Translator and the Front-End
Implemented as plug-in to TIOA front-end
Dynamically loaded to process AST & generate corresponding UPPAAL specification.

4. Integration with Front-End

5. UPPAAL-Compliant Subset of TIOA
Variable types: only Int, Nat, Real, Const, Boolean and Enumeration are allowed for now
Internal actions don't have parameters
Effect statements are only assignments
Trajectories limited to d(t)=1
Locations enumeration type defines TA states

6. Translation Scheme TIOA states translated to UPPAAL variables
TIOA actions translated to UPPAAL transitions
Composite TIOA actions in different primitive automata with same name translated to synchronized transitions in UPPAAL
TIOA locations translated to UPPAAL states
Stop-When conditions become state invariants

7. Train-Crossing Example
Models a train approaching a crossing. After light is signaled, gate is lowered for train to cross. Each action takes place with a certain urgency.

8. Train-Crossing Timed Automaton

9. Train-Crossing Example in TIOA
vocabulary Locations
types Location
enumeration [begin, light, gate]
automaton Train
imports Locations
signature
internal coming, approaching, passing
states
mode : Location := begin,
time : Real
transitions
internal coming
pre mode = begin /\ time > 2
eff mode := light; time := 0
internal approaching
pre mode = light /\ time > 5
eff mode := gate; time := 0
internal passing
pre mode = gate /\ time > 1
eff mode := begin; time := 0
trajectories
trajdef begin
invariant mode = begin
stop when time = 5
evolve d(time) = 1
trajdef light
invariant mode = light
stop when time = 10
trajdef gate
invariant mode = gate
stop when time = 2

10. Generated UPPAAL Code process Train{ clock time;
state begin {time<=5}, light {time<=10}, gate {time<=2};
init begin;
trans
begin -> light { guard time > 2; assign time := 0; },
light -> gate { guard time > 5; assign time := 0; },
gate -> begin { guard time > 1; assign time := 0; }; }
system Train;

11. Fischer Protocol

12. Fischer in TIOA vocabulary ProgramCounter1 types Location enumeration
[idle, request, wait, critical]
automaton Fischer(pid : Const)
imports ProgramCounter1
signature
internal try, abort, enter
input read_response(id : Int)
output write_set(id : Int),
write_exit(id : Int)
states
mode : Location := idle,
turn : Int,
time : Real
transitions
input read_response(id)
eff turn := id
internal try
pre mode = idle /\ turn = 0
eff mode := request; time := 0
output write_set(id)
pre mode = request /\ id = pid
eff mode := wait; time := 0
internal retry
pre mode = wait /\ time > 2 /\ turn ~= pid
eff mode := idle
internal enter
pre mode = wait /\ time > 2 /\ turn = pid
eff mode := critical
output write_exit(id)
pre mode = critical /\ id = 0
trajectories
trajdef request
invariant mode = request
stop when time = 2
evolve d(time) = 1
trajdef traj

13. Fischer continued input write_set(id) automaton SharedVar signature
input write_set(id : Int),
write_exit(id : Int)
output read_response(id : Int)
states
turn : Int := 0,
send : Bool := true,
t : Real
transitions
output read_response(id)
pre send = true /\ id = turn
eff send := false
input write_set(id)
eff send := true; turn := id
input write_exit(id)
trajectories
trajdef traj
evolve d(t) = 1
automaton sys
components
fischer1 : Fischer(1);
fischer2 : Fischer(2);
fischer3 : Fischer(3);
SharedVar

14. Generated UPPAAL Code int id; urgent broadcast chan read_response;
broadcast chan write_set,write_exit;
process Fischer(const pid){
int turn;
clock time;
state idle, request {time <=2}, wait, critical;
init idle;
trans
idle > idle { sync read_response?; assign turn := id; },
request -> request { sync read_response?; assign turn := id; },
wait > wait { sync read_response?; assign turn := id; },
critical -> critical { sync read_response?; assign turn := id; },
idle > request { guard turn == 0; assign time := 0; },
request -> wait { guard sync write_set!; assign id := pid,time := 0; },
wait > idle { guard time > 2 && turn != pid; },
wait > critical { guard time > 2 && turn == pid; },
critical -> idle { guard sync write_exit!; assign id := 0; }; }

15. UPPAAL Code continued process SharedVar{ int turn := 0;
bool send := true;
clock t;
state default;
init default;
trans
default -> default { guard send == true; sync read_response!;
assign id := turn,send := false; },
default -> default { sync write_set?; assign send := true,turn := id; },
default -> default { sync write_exit?; assign send := true,turn := id; };}
fischer1 := Fischer(1);
fischer2 := Fischer(2);
fischer3 := Fischer(3);
system fischer1, fischer2, fisher3, ShardVar;

16. Future work Semantics checking for UPPAAL compliancy
Monte Carlo model checking for TIOA
Efficient sampling of transition graphs

17. Efficient Sampling of Transition Graphs
Basic idea (tree growth in nature):
From all root-successors, randomly walk to a leaf
Then repeat the following:
Uniformly pick a node from the ones visited
Randomly walk to a leaf from this node
Check property on all intermediate nodes

18. Fischer Protocol (buggy)
Processes
Tree Sampling
UPPAAL 2
0.002
0.021 4
0.008
0.041 8
0.083
1.280 12
0.524
18.61 16
1.018
oom

19. Bang & Olufson Audio/Video Protocol
Senders
Tree Sampling
UPPAAL 2
0.041
0.174 3 14
1.05 4 32
10.1 5
8(min)
2(min) 6
37(min)
oom