1. Test & Verification Verification Kim G. Larsen

2. TOV 2002Kim G. Larsen 2 Research Profile Distributed Systems & Semantics Unit Semantic Models concurrency, mobility, objects real-time, hybrid systems Validation & Verification algorithms & tools Construction real-time & network systems

3. TOV 2002Kim G. Larsen 3 BRICS Machine Basic Research in Computer Science 30+40+40 Millkr 100 Aalborg Aarhus Tools Other revelvant projects UPPAAL, VHS, VVS, WOODDES

4. TOV 2002Kim G. Larsen 4 Tools and BRICS Logic Temporal Logic Modal Logic MSOL Algorithmic (Timed) Automata Theory Graph Theory BDDs Polyhedra Manipulation Semantics Concurrency Theory Abstract Interpretation Compositionality Models for real-time & hybrid systems HOL TLP Applications PVS ALF SPIN visualSTATEUPPAAL

5. TOV 2002Kim G. Larsen 5 A very complex system Klaus Havelund, NASA

6. TOV 2002Kim G. Larsen 6 Rotterdam Storm Surge Barrier

7. TOV 2002Kim G. Larsen 7 Spectacular Bugs z ARIANE-5 z INTEL Pentium II floating-point division 470 Mill US $ z Baggage handling system, Denver 1.1 Mill US $/day for 9 months z Mars Pathfinder z Radiation theraphy, Therac-25 z ……. More in JPK, CW

8. TOV 2002Kim G. Larsen 8 Embedded Systems SyncMaster 17GLsi Telephone Tamagotchi Mobile Phone Digital Watch

9. TOV 2002Kim G. Larsen 9 A simple program Int x Process INC do :: x x:=x+1 od Process DEC do :: x>0 --> x:=x-1 od Process RESET do :: x=200 --> x:=0 od fork INC; fork DEC; fork RESET Int x Process INC do :: x x:=x+1 od Process DEC do :: x>0 --> x:=x-1 od Process RESET do :: x=200 --> x:=0 od fork INC; fork DEC; fork RESET Which values may x take ? Questions/Properties: E<>(x>1000) E<>(x>2000) A[](x<=2000) E<>(x<0) A[](x>=0) Possibly Always

10. TOV 2002Kim G. Larsen 10 Introducing, Detecting and Repairing Errors Liggesmeyer 98

11. TOV 2002Kim G. Larsen 11 Introducing, Detecting and Repairing Errors Liggesmeyer 98

12. TOV 2002Kim G. Larsen 12 Suggested Solution? Model based validation, verfication and testing of software and hardware

13. TOV 2002Kim G. Larsen 13 Verification & Validation Design ModelSpecification Analysis Implementation Testing

14. TOV 2002Kim G. Larsen 14 Verification & Validation Design ModelSpecification Verification & Refusal Analysis Validation Implementation Testing UML SDL

15. TOV 2002Kim G. Larsen 15 Verification & Validation Design ModelSpecification Verification & Refusal Analysis Validation Implementation Testing UML SDL Model Extraction Automatic Code generation

16. TOV 2002Kim G. Larsen 16 Verification & Validation Design ModelSpecification Verification & Refusal Analysis Validation Implementation Testing UML Automatic Code generation Automatic Test generation SDL Model Extraction

17. TOV 2002Kim G. Larsen 17 How? Unified Model = State Machine! a b x y a? b? x! y!b? Control states Input ports Output ports

18. TOV 2002Kim G. Larsen 18 Tamagotchi A C Health=0 or Age=2.000 B PassiveFeeding Light Clean PlayDisciplineMedicine Care Tick Health:=Health-1; Age:=Age+1 A A A A A A A A Meal Snack B B ALIVE DEAD Health:= Health-1

19. TOV 2002Kim G. Larsen 19 SYNCmaster

20. TOV 2002Kim G. Larsen 20 Digital Watch

21. TOV 2002Kim G. Larsen 21 The SDL Editor Process level

22. TOV 2002Kim G. Larsen 22 SPIN, Gerald Holzmann AT&T

23. TOV 2002Kim G. Larsen 23 visualSTATE zHierarchical state systems zFlat state systems zMultiple and inter- related state machines zSupports UML notation zDevice driver access VVS w Baan Visualstate, DTU (CIT project)

24. TOV 2002Kim G. Larsen 24 ESTEREL

25. TOV 2002Kim G. Larsen 25 UPPAAL

26. TOV 2002Kim G. Larsen 26 ‘State Explosion’ problem a cb 1 2 43 1,a 4,a 3,a4,a 1,b2,b 3,b4,b 1,c2,c 3,c4,c All combinations = exponential in no. of components M1 M2 M1 x M2 Provably theoretical intractable

27. TOV 2002Kim G. Larsen 27 Train Simulator 1421 machines 11102 transitions 2981 inputs 2667 outputs 3204 local states Declare state sp.: 10^476 BUGS ? VVS visualSTATE Our techniuqes has reduced verification time with several orders of magnitude (ex 14 days to 6 sec)

28. TOV 2002Kim G. Larsen 28 Tool Support (model checking) System Description A Requirement F Yes, Prototypes Executable Code Test sequences No! Debugging Information Tools: UPPAAL, visualSTATE, ESTEREL, SPIN, Statemate, FormalCheck, VeriSoft, Java Pathfinder,… TOOL

29. VVS Verification and Validation of Large Systems DTU, Aalborg, Baan Visualstate URLs://www.visualSTATE.com //www.it.dtu.dk/~jst/vvs/

30. TOV 2002Kim G. Larsen 30 BAAN VisualSTATE Tidligere BEOLOGIC salesPLUS visualSTATE Beologic’s Products: salesPLUS visualSTATE 1980-95: Independent division of B&0 1995- : Independent company B&O, 2M Invest, Danish Municipal Pension Ins. Fund Customers: ABB B&O Daimler-Benz Ericson DIAX ESA/ESTEC FORD Grundfos LEGO PBS Siemens ……. (approx. 90) Verification Problems: 1.000 components 10 400 states Our techniques has reduced verification by an order of magnitude (from 14 days to 6 sec) Embedded Systems Simple Model Verification of Std. Checks Explicit Representation (STATEEXPLOSION) Code Generation

31. TOV 2002Kim G. Larsen 31 visualSTATE 4.0 Product Modules zNavigator zPrototyper yGraphical Simulation of human interface panels zPresenter yPrototyper for distribution zDesigner yDiagram Designer yMatrix Designer yText Editor zTester yValidator xSimulation xAnimation xAnalysis yVerificator xStatic verification xDynamic verification zGenerator yCoder yDocumentor

32. TOV 2002Kim G. Larsen 32 visualSTATE Prototyper A virtual prototype of a mobile telephone zGUI Builder zGUI Executer zPick’n place of symbols zNo manual coding zCustom designed objects yActiveX controls yGraphics libraries

33. TOV 2002Kim G. Larsen 33 visualSTATE Designer zHierarchical state systems zFlat state systems zMultiple and inter- related state machines zSupports UML notation zDevice driver access

34. TOV 2002Kim G. Larsen 34 zNo local nor global dead-ends zNo never interpreted events zNo fired actions zNo conflicting transactions zNo unreachable states zAll combinations are checked! visualSTATE Tester Verification 100% Tested! No bugs allowed!

35. TOV 2002Kim G. Larsen 35 Train Simulator 1421 machines 11102 transitions 2981 inputs 2667 outputs 3204 local states Declare state sp.: 10^476 BUGS ? VVS

36. TOV 2002Kim G. Larsen 36 Experimental Breakthroughs Machine: 166 MHz Pentium PC with 32 MB RAM ---: Out of memory, or did not terminate after 3 hours. VVS project BRICS/Aalborg, DTU, BAAN visualSTATE

37. TOV 2002Kim G. Larsen 37 Experimental Breakthroughs Patented Machine: 166 MHz Pentium PC with 32 MB RAM ---: Out of memory, or did not terminate after 3 hours. Our techniques have reduced verification time with several orders of magnitude (ex from 14 days to 6 sec)

38. UPPAAL Modelling and Verification of Real Time systems UPPAAL2k > 800 users > 35 countries UPPAAL2k > 800 users > 35 countries

39. TOV 2002Kim G. Larsen 39 Collaborators @UPPsala yWang Yi yJohan Bengtsson yPaul Pettersson yFredrik Larsson yAlexandre David yTobias Amnell yOliver Möller @AALborg yKim G Larsen yArne Skou yPaul Pettersson yCarsten Weise yKåre J Kristoffersen yGerd Behrman yThomas Hune yOliver Möller yNicky Oliver Bodentien yLasse Poulsen @Elsewhere yDavid Griffioen, Ansgar Fehnker, Frits Vandraager, Klaus Havelund, Theo Ruys, Pedro D’Argenio, J-P Katoen, J. Tretmans, Judi Romijn, Ed Brinksma, Franck Cassez, Magnus Lindahl, Francois Laroussinie, Patricia Bouyer, Augusto Burgueno, H. Bowmann, D. Latella, M. Massink, G. Faconti, Kristina Lundqvist, Lars Asplund, Justin Pearson...

40. TOV 2002Kim G. Larsen 40 Dec’96Sep’98

41. TOV 2002Kim G. Larsen 41 Dec’96Sep’98 from 7.5 hrs / 527 MB on ONYX with 2GB (4Mill DKK) to 12.75 sec / 2.1 MB on Pentium 150 MHz, 32 MB or Every 9 month 10 times better performance!

42. TOV 2002Kim G. Larsen 42 Hybrid & Real Time Systems Plant Continuous Controller Program Discrete Control Theory Computer Science Eg.: Pump Control Air Bags Robots Cruise Control ABS CD Players Production Lines Real Time System A system where correctness not only depends on the logical order of events but also on their timing Real Time System A system where correctness not only depends on the logical order of events but also on their timing sensors actuators Task

43. TOV 2002Kim G. Larsen 43 Construction of UPPAAL models Plant Continuous Controller Program Discrete sensors actuators Task a cb 1 2 43 a cb 1 2 43 1 2 43 1 2 43 a cb UPPAAL Model Model of environment (user-supplied) Model of tasks (automatic?)

44. TOV 2002Kim G. Larsen 44 Intelligent Light Control OffLightBright press? WANT: if press is issued twice quickly then the light will get brighter; otherwise the light is turned off.

45. TOV 2002Kim G. Larsen 45 Intelligent Light Control OffLightBright press? Solution: Add real-valued clock x X:=0 X<=3 X>3

46. TOV 2002Kim G. Larsen 46 Timed Automata n m a Alur & Dill 1990 Clocks: x, y x 3 x := 0 Guard Boolean combination of integer bounds on clocks and clock-differences. Reset Action perfomed on clocks Transitions ( n, x=2.4, y=3.1415 ) ( n, x=3.5, y=4.2415 ) e(1.1) ( n, x=2.4, y=3.1415 ) ( m, x=0, y=3.1415 ) a State ( location, x=v, y=u ) where v,u are in R Action used for synchronization

47. TOV 2002Kim G. Larsen 47 n m a Clocks: x, y x 3 x := 0 Transitions ( n, x=2.4, y=3.1415 ) ( n, x=3.5, y=4.2415 ) e(1.1) ( n, x=2.4, y=3.1415 ) e(3.2) x<=5 y<=10 Location Invariants g1 g2 g3 g4 Timed Automata Invariants Invariants ensure progress!!

48. TOV 2002Kim G. Larsen 48 The UPPAAL Model = Networks of Timed Automata + Integer Variables +…. l1 l2 a! x>=2 i==3 x := 0 i:=i+4 m1 m2 a? y<=4 …………. Two-way synchronization on complementary actions. Closed Systems! Two-way synchronization on complementary actions. Closed Systems! (l1, m1,………, x=2, y=3.5, i=3,…..) (l2,m2,……..,x=0, y=3.5, i=7,…..) (l1,m1,………,x=2.2, y=3.7, I=3,…..) 0.2 tau Example transitions If a URGENT CHANNEL

49. TOV 2002Kim G. Larsen 49 LEGO Mindstorms/RCX  Sensors: temperature, light, rotation, pressure.  Actuators: motors, lamps, zVirtual machine: y10 tasks, 4 timers, 16 integers. zSeveral Programming Languages: yNotQuiteC, Mindstorm, Robotics, legOS, etc. 3 input ports 3 output ports 1 infra-red port

50. TOV 2002Kim G. Larsen 50 First UPPAAL model Sorting of Lego Boxes Conveyer Belt Exercise: Design Controller so that only black boxes are being pushed out Boxes Piston Black red 9 18 81 90 99 Blck Rd remove eject Controller Ken Tindell MAINPUSH

51. TOV 2002Kim G. Larsen 51 NQC programs task PUSH{ while(true){ wait(Timer(1)>DELAY && active==1); active=0; Rev(OUT_C,1); Sleep(8); Fwd(OUT_C,1); Sleep(12); Off(OUT_C); } task PUSH{ while(true){ wait(Timer(1)>DELAY && active==1); active=0; Rev(OUT_C,1); Sleep(8); Fwd(OUT_C,1); Sleep(12); Off(OUT_C); } int active; int DELAY; int LIGHT_LEVEL; int active; int DELAY; int LIGHT_LEVEL; task MAIN{ DELAY=75; LIGHT_LEVEL=35; active=0; Sensor(IN_1, IN_LIGHT); Fwd(OUT_A,1); Display(1); start PUSH; while(true){ wait(IN_1<=LIGHT_LEVEL); ClearTimer(1); active=1; PlaySound(1); wait(IN_1>LIGHT_LEVEL); } task MAIN{ DELAY=75; LIGHT_LEVEL=35; active=0; Sensor(IN_1, IN_LIGHT); Fwd(OUT_A,1); Display(1); start PUSH; while(true){ wait(IN_1<=LIGHT_LEVEL); ClearTimer(1); active=1; PlaySound(1); wait(IN_1>LIGHT_LEVEL); }

52. UPPAAL Demo

53. TOV 2002Kim G. Larsen 53 From RCX to UPPAAL zModel includes Round-Robin Scheduler. zCompilation of RCX tasks into TA models. zPresented at ECRTS 2000 Task MAIN

54. TOV 2002Kim G. Larsen 54 The Production Cell Course at DTU, Copenhagen Production Cell

55. TOV 2002Kim G. Larsen 55 Train Crossing River Crossing Gate Stopable Area [10,20] [7,15] Queue [3,5]

56. TOV 2002Kim G. Larsen 56 Train Crossing River Crossing Gate Stopable Area [10,20] [7,15] Queue [3,5] appr, stop leave go empty nonempty hd, add,rem el Communication via channels and shared variable.

57. TOV 2002Kim G. Larsen 57 Case Studies: Protocols zPhilips Audio Protocol [HS’95, CAV’95, RTSS’95, CAV’96 ] zCollision-Avoidance Protocol [SPIN’95] zBounded Retransmission Protocol [TACAS’97] zBang & Olufsen Audio/Video Protocol [RTSS’97] zTDMA Protocol [PRFTS’97] zLip-Synchronization Protocol [FMICS’97] zMultimedia Streams [DSVIS’98] zATM ABR Protocol [CAV’99] zABB Fieldbus Protocol [ECRTS’2k] zIEEE 1394 Firewire Root Contention (2000)

58. TOV 2002Kim G. Larsen 58 Case-Studies: Controllers zGearbox Controller [TACAS’98] zBang & Olufsen Power Controller [RTPS’99,FTRTFT’2k] zSIDMAR Steel Production Plant [RTCSA’99, DSVV’2k] zReal-Time RCX Control-Programs [ECRTS’2k] zExperimental Batch Plant (2000) zRCX Production Cell (2000)

59. TOV 2002Kim G. Larsen 59 Timed Automata in U PPAAL zTimed (Safety) Automata + urgent actions + urgent locations + committed locations + data-variables (with bounded domains) + arrays of data-variables + constants + guards and assignments over data-variables and arrays… + templates with local clocks, data-variables, and constants.

60. TOV 2002Kim G. Larsen 60 Declarations in U PPAAL clock x 1, …, x n ; int i 1, …, i m ; chan a 1, …, a o ; const c 1 n 1, …, c p n p ; Examples: clock x, y; int i, J0; int[0,1] k[5]; const delay 5, true 1, false 0; Array k of five booleans.

61. TOV 2002Kim G. Larsen 61 Timed Automata in U PPAAL n m a x 3 x := 0 x<=5 y<=10 g1 g2 g3 g4 clock natural number and clock guards data guards clock assignments location invariants

62. TOV 2002Kim G. Larsen 62 Urgent Channels urgent chan hurry; Informal Semantics: There will be no delay if transition with urgent action can be taken. Restrictions: No clock guard allowed on transitions with urgent actions. Invariants and data-variable guards are allowed.

63. TOV 2002Kim G. Larsen 63 Urgent Locations Click “Urgent” in State Editor. Informal Semantics: No delay in urgent location. Note: the use of urgent locations reduces the number of clocks in a model, and thus the complexity of the analysis.

64. TOV 2002Kim G. Larsen 64 Committed Locations Click “Committed” in State Editor. Informal Semantics: No delay in committed location. Next transition must involve automata in committed location. Note: the use of committed locations reduces the number of clocks in a model, and allows for more space and time efficient analysis.

65. TOV 2002Kim G. Larsen 65 UPPAAL Specification Language A[] p (AG p) E<> p (EF p) p::= a.l | g d | g c | p and p | p or p | not p | p imply p | ( p ) clock guardsdata guardsprocess location

66. TOV 2002Kim G. Larsen 66 CSMA/CD protocol – MAC layer send - service provided by Mac which reacts by transmitting a message, rec - (receive) service provided by Mac, indicates that a message is ready to be received, b - (begin) Mac begins message transmission to M, e - (end) Mac terminates message transmission to M, br - (begin receive) M begins message delivery to Mac, er - (end receive) M terminates message delivery to Mac, b - (collision) Mac is notified that a collision has occurred on M. EVENTS

67. Philips Bounded Retransmission Protocol [D’Argenio et.al. 97]

68. TOV 2002Kim G. Larsen 68 Protocol Overview zProtocol developed by Philips. zTransfer data between Audio/Video components via infra-red communication. zData files sent in smaller chunks. zProblem: Unreliable communication medium. zSender retransmit if receiver respond too late. zReceiver abort if sender sends too late.

69. TOV 2002Kim G. Larsen 69 Overview of BRP SenderReceiver SR K L Input: file = p 1, …, p n lossy Output: p 1, …, p n BRP pipi ack

70. TOV 2002Kim G. Larsen 70 How It Works  Sender input: file = p 1, …, p n.  S sends (p 1, FST, 0 ), (p 2, INC, 1 ), …, (p n-1, INC, 1 ), (p n, OK, 0 ).  R sends: ack, …, ack.  S retransmits p i if timeout.  Receiver recives: p 1, …, p n.  Sender and Receiver receives NOK or OK. whole file OK more parts will follow first part of file

71. TOV 2002Kim G. Larsen 71 BRP Model Overview SenderReceiver SR K L Input: file = p 1, …, p n ack (p i,INDication,abit ) lossy ok, nok, dk IND, ok, nok Output: p 1, …, p n BRP

72. TOV 2002Kim G. Larsen 72 The Lossy Media value-passing lossy = may drop messages one-place capacity delay

73. TOV 2002Kim G. Larsen 73 Bounded Retransmission  S sends a chunk pi and waits for ack from R. zIf timeout the chunk is retransmitted.  If too many timeout the transmission fails ( NOK is sent to Sender ).  If whole file successfully sent OK is sent to Sender.  Receiver is similar.

74. TOV 2002Kim G. Larsen 74 Process S

75. TOV 2002Kim G. Larsen 75 Process R

76. TOV 2002Kim G. Larsen 76 The Sender and Receiver

77. TOV 2002Kim G. Larsen 77 “If you want to know more” zTest & Verification yhttp://www.cs.auc.dk/~ejersbo/tov/Plan.html zBRICS@Aalborg yhttp://www.cs.auc.dk/research/FS/ zUPPAAL yhttp://www.uppaal.com zWOODDES, ATT (VHS): yhttp://www.docs.uu.se/docs/rtmv/wooddes/http://www.docs.uu.se/docs/rtmv/wooddes/ yhttp://www-verimag.imag.fr/VHS/main.html zStrategic Directions in Computing Research Formal Methods Working Group, ACM June 1996 yhttp://www.cs.cmu.edu/afs/cs/usr/wing/www/mit/mit.html