L8-9 ENGENEERING SUM Flashcards
● The system engineering V‐model
On the left hand side: The system definition processes from a general view of the user, through a decomposition of functionality, toward a specific design.
On the right hand side: The components of the system are gradually integrated and the result of integration is tested to measure how well it meets the user’s needs.
What are stakeholders? Give examples.
A stakeholder can be anyone with an interest in, or has an effect on, the outcome of the product. This includes customers that can be the system’s intended users, but also the persons who commission the construction of the system, called clients, sponsors, all responsible technical persons etc.
Functional vs nonfunctional requirements. You should be able to formulate a requirement.
Functional requirements specify what the system must do:
- The behavior of the system
- How it interacts with its users and other systems
- What capabilities it provides
- What information it consumers and delivers
Non-functional requirements are not directly concerned with the specific functions delivered by the system:
- They define how well the system must performs its functions
- Describe the system’s look and feel, its usability, performance, reliability, safety, affordability, maintainability, privacy etc.
- Constraints
o Define “under what conditions” the system must operate
Properties of a good system specification document
- Name
- Short description
- Precondition: prerequisites for successful execution
- Postcondition: system state after successful execution
- System state in case of error
- Actors
- Triger: events that initiate the use case
- Standard scenario: individual steps to be taken
- Alternative flow of events: deviation from the standard scenario
UML use case, state, activity diagrams. You should know how to draw a simple one.
A use case depicts the interactions between the system and the environment around the system, in particular human users and other systems. Use cases describe scenarios of operation of the system from the designer’s as opposed to customer’s perspective. Use cases are graphically represented in UML using a use case diagram.
State (transition) diagrams are graphical models suitable for defining the dynamic, temporal behavior of a system. They detail all the states, in which the system can be found, and the transitions between these states, triggered by certain events. A state diagram is a graph, with states as nodes, and state transitions as edges.
Activity models are another modeling instrument that visualizes the workflow of a use case. These models are appropriate when the system’s behavior changes not as a result of an event, but due to the end of an action, or activity. An activity diagram is a collection of nodes and arcs that starts with an initial node and ends with a final node. The nodes are the actions or activities. Activities are things that happen and cannot be broken further in smaller operations. When an activity node completes its execution, the flow of control passes immediately to the next activity node.
The definition of error, fault, failure. Examples.
○ A human error, also called mistake, is defined as a human action that produces an incorrect result.
○ A fault is a defect in the hardware or an incorrect step, process, or data definition in software. This is also called bug or defect.
○ A failure is the inability of a system or component to perform as required or intended.
An accident is an unplanned event that results in human death or injury.
The V‐model and testing levels
Waterfall, agile, test driven development: advantages and disadvantages
● What is a hazard and how to perform a hazard analysis using FTA, FMEA or STAMP Hazard
- Unwanted functionality
- Condition with the potential of causing or contributing to an accident.
Hazard analysis:
- identification of all known and foreseeable hazardous situations, together with their possible root causes.
- The risk of each identified hazard. The risk is calculated as the product between the probability that the hazard will happen and its severity, or impact.
- Risk evaluation is conducted, to decide whether the calculated risk of each hazard is acceptable, based on predefined acceptability criteria.
- If a risk is decided to be unacceptable, control measures must be taken to eliminate it or to mitigate it to an acceptable level. This is done by formulating an appropriate safety requirement.
- Manufacturers and regulators will have to check during safety testing activities whether the product satisfies all safety requirements. Safety requirements add new test scenarios and test cases to the test plan.
- After the product has been released, its safety must be continuously managed. During the operation and maintenance of the system, incidents in the field must be documented and reported back to the developers and safety regulating agencies.
Hazard analysis in system engineering always needs input from users and domain experts and can be performed through brainstorm sessions, or by using well-defined hazard analysis technique, such as failure mode and effects analysis (FMEA), fault tree analysis (FTA), or Systems-Theoretic Accident Model and Processes (STAMP)
Given a system, imagine an accident, a hazard, a casual scenario and a mitigation measure for it. Also, deduce from here a test scenario.
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● Explain how an automatic insulin pump works.
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What is a test case?
A set of input values, together with the corresponding expected output produced by the tested module.
Testing techniques (scenario based, BVA)
Boundary value analysis (BVA) is a systematic black box test generation technique, suitable for requirements that restrict a variable to a certain range. This method is based on the heuristics that often programming faults are introduced at the edges of valid intervals. If a variable x is restricted by requirements to a certain interval [xmin, xmax] and the minimum increment of the variable is 1, then the test inputs suggested by BVA are as follows: xmin, xmin + 1, a nominal value in the middle of the interval, xmax − 1 and xmax.
Equivalence partitioning (EP) is another black box test generation technique. This method tries to reduce the huge number of test inputs by dividing the input domain in equivalence classes. Two inputs belong to the same class, if there are reasons to believe that they are processed in the same way by the software
You should be able to formulate an ethical question related to a given pervasive
The “uncanny valley” is a characteristic dip in emotional response that happens when we encounter an entity that is almost, but not quite, huma
