CISC 844 In-class Exercise: Can you get there from here?

[The UML-RT model for Model RealTime used in this exercise can be found here]

Let S be a state machine. We define a runtime state of S to be a pair (ssc, val) where ssc is a stable state configuration of S and val is a mapping of all attributes of S to values. Consider the following state machine from Miro Samek in [Sam09] (part of Reading R2).

While viewing the state machine as a UML-RT state machine, answer the following questions.

  1. What is an example of a sequence of inputs that result in an 'unexpected message' message?
  2. What is the runtime state that the input sequence 'H, D, C, B' puts the machine into?
  3. What is the shortest sequence of inputs that puts the machine into the runtime state (<s,s2,s21,s211>, [foo=1])?
  4. What are examples of unreachable stable state configurations, i.e., stable state configurations for which there is no sequence of inputs that put the state machine into that configuration?
Last modified: Thu Feb 5 14:10:42 EST 2026