System Modelling 2019/2 -- Theoretical Questions 8
Example theoretical questions for practising for the 2nd mid-term exam in System Modelling. (In the mid-term exam, you get +1/4 point for each correct answer, -1/4 point for each incorrect ones, and 0 point for each question left out. You have to reach 50% of the possible points in this system. The Google Form is not able to implement this points system.)
1. A numerical variable …
1/a … is a variable for which the basic arithmetic operations are interpreted. *
1 point
1/b … can be ordered or unordered. *
1 point
1/c … 's relation to another numerical one can be visualized by a scatterplot. *
1 point
1/d … 's value distribution is usually visualized by parallel coordinates (also called bar charts). *
1 point
2. The utilization of a (non-overloaded) system is maximal exactly then, when …
2/a … the arrival rate is equal to the maximum throughput. *
1 point
2/b … the throughput is equal to the maximum throughput. *
1 point
2/c … the utilization of each component is 100%. *
1 point
2/d … the system is in stable state. *
1 point
3. The Little's law …
3/a … 's form, which was discussed at the lectures, is valid only for the stable state of the system. *
1 point
3/b … is only applicable for single server systems. *
1 point
3/c … is also valid for systems that are described by process models with multiple activities. *
1 point
3/d … estimates the execution time with the reciprocal of the popularity of the functions. *
1 point
4. If we make our process model well-structured, that way we can avoid ...
4/a … the formation of a deadlock at the join nodes. *
1 point
4/b … non-deterministic behaviour. *
1 point
4/c … not fully specified behaviour. *
1 point
4/d … endless loops. *
1 point
5. A deadlock …
5/a … is a state of the system, from which it cannot move to another state according the model, and it cannot show further activity. *
1 point
5/b … inevitably occurs at each join node. *
1 point
5/c … inevitably occurs in each hierarchical state machine. *
1 point
5/d … can only occur in flow end (termination) node of a process. *
1 point
6. A livelock (endless loop) …
6/a … means that the system can only leave the loop if it diverges from its specification described in the model (e.g. we restart it). *
1 point
6/b … can be avoided by building well-structured models only. *
1 point
6/c … may occur e.g. if from the guard conditions of the decision node of the loop always that one will be true, which belongs to the branch leading back to the beginning of the loop. *
1 point
6/d … inevitably occurs in each non-deterministic model. *
1 point
7. A (functional) test case always includes …
7/a … the test coverage. *
1 point
7/b … the test input. *
1 point
7/c … a test oracle specified as a state machine. *
1 point
7/d … a concrete, expected (reference) sequence of outputs, or an evaluable property of it. *
1 point
8. A test oracle …
8/a … can always exactly tell, what is the expected output. *
1 point
8/b … aims at detecting cases, in which the system gets invalid input. *
1 point
8/c … can always tell without execution, whether the test can successfully run on the system, when it is ready. *
1 point
8/d … is always stateless, it evaluates the output signals in themselves, independent of the former inputs and outputs. *
1 point
9. 100% test coverage …
9/a … is only valid for one metrics, e.g. the complete state coverage does not guarantee a complete transition coverage. *
1 point
9/b .. can only be reached with self-testing systems. *
1 point
9/c … guarantees the absence of any errors (when each test case run successfully), because it means that all possible behaviours were checked. *
1 point
9/d … means that the given test case touches each part of the system that were touched by any test cases of the given test suite. *
1 point
10. Model checking …
10/a … checks whether the model satisfies the requirements. *
1 point
10/b … is one kind of testing. *
1 point
10/c … is considered a dynamic analysis. *
1 point
10/d … makes an exhaustive analysis i.e. it checks all possible behaviours. *
1 point
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