Computer Science 223 Discussion Questions

Alhir, Pages 98-105

Discussion questions submitted for pages 98-105 of Alhir:


  1. What is the purpose of a statechart and what advantages does it hold over other kind of charts that we use? taha
  2. In Fig 4-30, there are two arrows coming from assigned, making a circle, and going back to assigned. I imagine it's some kind of a loop for assigning tasks but why there are two arrows not just one? Dessislava Dimova
  3. For the sake of practicality, couldn't use and statecharts be combined? (assuming the project does not have too many classes) todd
  4. Why is the distinction between assigned and not assigned important enough to merit a state? It seems better to me to have resources have an assignment value 0 or more tasks that it is assigned to, and not bother with the extra state.
  5. If statechart diagrams and activity diagrams are similar, does that mean one can replace the other? If not, what decides which is preferred to which? (Raz Magar)
  6. What happens when statechart diagrams get too complex to notate efficiently?
  7. When would we use StateChart Diagrams and when would we use Activity Diagrams? ~yasir
  8. How are statecharts different from collaboration diagrams? -Peter Likarish
  9. Can there be a special case in statechart diagram where the final state is reached and the object not destroy? Anthony
  10. Statecharts diagram the behavior of a class in response to external stimuli. What exactly is the scope of external stimuli? Does it include other classes, or users, or both? (Sam Vanderhyden)


  1. What is the precise definition of a superstate? --Khong
  2. How do substates in a superstatechart diagram relate or communicate with each other? George Yeboah
  3. Does a superstate create a hierarchical way organizing the state of an object?
  4. How do we decide to make substate statechart diagram? Can it be incorporated in statechart diagram? --Hisako

Types of Diagrams

  1. How do Component diagrams and Deployment diagrams differ from each other? (Raz Magar)
  2. What is the difference between Component and Deployment diagrams? - Elias Vafiadis
  3. What is the relationship between Component Diagrams and Deployment Diagrams? ~yasir
  4. What will the deployment diagram and component diagram represent in the code? Steve F
  5. Alhir says that activity diagrams "are part of the dynamic model of a system" (104), but couldn't all of the diagrams presented in this section be considered part of the dynamic model? --Khong
  6. is there another way to show an object is used by an action that isn't as messy on paper in a Resource Activity Diagram?
  7. Can you clarify as to how deployment diagrams work?
  8. Are there solid arrows used in the component diagram? Anthony
  9. What are the differences between activity diagrams and sequence diagrams? Patrick Dowd
  10. What structural differences exists between statechart diagrams and activity diagrams? George Yeboah
  11. During class, could we create the activity chart for the appointment class? todd
  12. What is the use of component diagrams? The context of the diagram seems too obvious to be actually useful. --Hisako
  13. What exactly is object code in the component diagrams? (Sam Vanderhyden)

Additional Questions

  1. When do splitting of control and synchronization of control actually happen? Patrick Dowd
  2. Is it necessary for us to keep rack of the activity or inactivity of all objects? It seems that many of them will not affect the system as they become active or inactive. Steve F.
  3. Can you describe 'splitting of control' on page 100 a bit more? -Kensler
  4. We have learned about a ton of diagramming techniques. If a project is being designed with UML, how many are actually used for a given project? (1?, more than 1?, most?) -Peter Likarish
  5. What is splitting of control? - Elias Vafiadis
  6. Is package to class, what class is to object? Dessislava Dimova
  7. Could you give examples of synchronization of control. taha
  8. How extensively should swim lanes be used? Is there a set of them for every interaction between more than one class? In how much detail do they need to be drawn out in an average case?
  9. Can you go over transitions in more detail? -Kensler
  10. What does synchronization of control mean?
  11. What is the difference between source code, object code, and execution code?

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