Timed Automata – Real-time Systems MCQs

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1. What is a timed automaton primarily used for?
(A) Modeling functional correctness
(B) Modeling time-dependent system behavior
(C) Database transaction control
(D) Compiler optimization

2. Who introduced the concept of timed automata?
(A) Leslie Lamport
(B) Alur and Dill
(C) Tony Hoare
(D) Edsger Dijkstra

3. Which component is added to finite automata in timed automata?
(A) Threads
(B) Variables
(C) Clocks
(D) Queues

4. What do clocks in timed automata measure?
(A) Memory usage
(B) Execution cost
(C) CPU frequency
(D) Elapsed time

5. Which of the following is a key characteristic of clocks in timed automata?
(A) Continuous real-valued time
(B) Boolean values
(C) Discrete values only
(D) Random increments

6. What is a clock constraint in timed automata?
(A) A scheduling rule
(B) A memory limit
(C) A condition on clock values
(D) A process priority

7. Which symbol is commonly used in clock constraints?
(A) =
(B) ∧
(C) ≤
(D) →

8. What happens to clocks during a reset?
(A) They stop progressing
(B) They are set to zero
(C) They are assigned infinity
(D) They double in value

9. Which element specifies allowable clock values in a state?
(A) Guard
(B) Transition
(C) Invariant
(D) Label

10. Guards in timed automata are associated with:
(A) Transitions
(B) Clocks only
(C) States
(D) Events

11. What does an invariant violation cause?
(A) Deadlock
(B) Immediate transition
(C) State exit
(D) Time stop

12. Which type of time progression is allowed in timed automata?
(A) Discrete only
(B) Both discrete and continuous
(C) Continuous only
(D) Random

13. Which formalism is timed automata an extension of?
(A) Petri nets
(B) Pushdown automata
(C) Turing machines
(D) Finite automata

14. What is a location in timed automata equivalent to?
(A) State
(B) Thread
(C) Process
(D) Clock

15. Which operation is NOT allowed on clocks?
(A) Reset
(B) Comparison
(C) Progress with time
(D) Addition of two clocks

16. What type of system is best modeled using timed automata?
(A) Batch processing systems
(B) Text editors
(C) File systems
(D) Real-time embedded systems

17. Which property can be verified using timed automata?
(A) Memory fragmentation
(B) Deadlock freedom with time constraints
(C) Code readability
(D) Disk throughput

18. What does reachability analysis determine?
(A) Reachable states under timing constraints
(B) Maximum clock value
(C) CPU usage
(D) Scheduling order

19. Which tool is commonly used for timed automata verification?
(A) UPPAAL
(B) NS-3
(C) MATLAB
(D) Wireshark

20. Timed automata are mainly used in which verification technique?
(A) Simulation only
(B) Testing only
(C) Model checking
(D) Compilation

21. What does a transition in timed automata represent?
(A) State change possibly with clock reset
(B) Time delay only
(C) Clock creation
(D) Process termination

22. Which type of clock constraint is allowed?
(A) x + y ≤ 5
(B) x − y ≥ 3
(C) x ≤ 5
(D) x × y < 10

23. What is a timed trace?
(A) Sequence of states with time stamps
(B) Sequence of instructions
(C) Memory dump
(D) Event log without time

24. Which feature makes timed automata suitable for real-time analysis?
(A) Nondeterminism
(B) Clock synchronization
(C) High-level abstraction
(D) Explicit modeling of time

25. Which of the following is NOT a component of timed automata?
(A) Stack
(B) Clocks
(C) Invariants
(D) Locations

26. What does nondeterminism allow in timed automata?
(A) Infinite clocks
(B) Random clock resets
(C) Multiple possible transitions
(D) Undefined states

27. Which condition must hold for a transition to fire?
(A) Invariant must be false
(B) Guard must be satisfied
(C) Clock must stop
(D) Time must reset

28. Which real-time constraint can be modeled using invariants?
(A) Minimum delay
(B) Maximum allowed time in a state
(C) Event priority
(D) Task dependency

29. Timed automata clocks progress when:
(A) System is in a location
(B) System is idle
(C) Transition occurs
(D) Reset happens

30. Which logic is often used with timed automata?
(A) Propositional logic
(B) Timed Computation Tree Logic
(C) Linear Temporal Logic
(D) Predicate logic

31. What is the main limitation of timed automata?
(A) Too expressive
(B) No real-time support
(C) Lack of tools
(D) State space explosion

32. Which approach helps reduce state explosion?
(A) Overclocking
(B) Manual inspection
(C) Random testing
(D) Abstraction

33. Which system behavior is captured by clock invariants?
(A) Ordering of events
(B) Memory usage
(C) Maximum time delay
(D) Task priority

34. What does a location invariant restrict?
(A) Transitions only
(B) Guard evaluation
(C) Reset behavior
(D) Clock progression in a state

35. Which is a typical application of timed automata?
(A) Web page design
(B) Network protocol verification
(C) Image processing
(D) Game graphics

36. Which type of clock is used in timed automata?
(A) Discrete clock
(B) Logical clock
(C) System clock
(D) Real-valued clock

37. What happens if time cannot progress due to invariants?
(A) Normal execution
(B) Transition ignored
(C) Deadlock
(D) Clock reset

38. Which property ensures an event happens before a deadline?
(A) Liveness
(B) Safety
(C) Timeliness
(D) Fairness

39. Which modeling aspect differentiates timed automata from FSMs?
(A) Inputs
(B) Outputs
(C) Time constraints
(D) Alphabet

40. What is zone-based analysis used for?
(A) Memory allocation
(B) Code optimization
(C) Representing clock constraints efficiently
(D) Event scheduling

41. Which of the following is a verification question in timed automata?
(A) Is a deadline always met?
(B) Is memory allocated?
(C) Is code optimized?
(D) Is file closed?

42. Timed automata transitions are triggered by:
(A) Time only
(B) Memory access
(C) Events and time conditions
(D) CPU interrupts only

43. What does synchronisation allow in timed automata networks?
(A) Shared memory
(B) Coordinated transitions
(C) Clock deletion
(D) Priority inversion

44. Which system type often uses networks of timed automata?
(A) Single-thread programs
(B) Distributed real-time systems
(C) Text processing systems
(D) Standalone utilities

45. What is a run in timed automata?
(A) Compilation phase
(B) Testing script
(C) Debugging process
(D) Execution sequence with timing