Chapter 10: Dependable Systems

Question 1

What is dependability?

Answer 1

Dependability reflects a system’s trustworthiness and the degree of user confidence, covering attributes like availability, reliability, safety, security, and resilience

Question 2

Define availability

Answer 2

Availability is the probability that a system will be operational and able to deliver requested services at any point in time

Question 3

Explain reliability

Answer 3

Explain reliabilityReliability is the probability of failure-free operation over a specified time, in a given environment, for a specific purpose

Question 4

What is safety in terms of dependability?

Answer 4

Safety is a judgment of how likely it is that the system will cause damage to people or its environment

Question 5

Define security in dependability

Answer 5

Security is the system’s ability to protect itself against deliberate or accidental intrusion

Question 6

Explain resilience

Answer 6

Resilience is the ability of the system to resist and recover from damaging events

Question 7

What are sociotechnical systems?

Answer 7

Sociotechnical systems involve software, hardware, and human operators as interdependent components, operating with a social or organizational purpose in a complex and changing environment

Question 8

What challenges do sociotechnical systems pose for dependability engineering?

Answer 8

Challenges include complexity, diversity, uncertainty, emergence, and evolution

Question 9

How can sociotechnical systems be modeled?

Answer 9

Sociotechnical systems can be modeled using various techniques, such as system diagrams, context models, interaction models, or structural models

Question 10

What are some techniques for analyzing sociotechnical systems?

Answer 10

Techniques include hazard analysis, risk analysis, fault tree analysis, and event tree analysis

Question 11

Define critical systems

Answer 11

Critical systems are systems whose failure may result in injury, environmental damage, or extensive economic losses. They can be safety-critical, mission-critical, or business-critical

Question 12

What is critical systems engineering?

Answer 12

Critical systems engineering involves activities such as requirements engineering, design engineering, verification and validation, configuration management, and quality management to develop dependable critical systems

Question 13

Name some methods for ensuring dependability in critical systems

Answer 13

Methods include formal methods, fault tolerance techniques, diversity techniques, and process improvement techniques

Question 14

Why are dependable systems important?

Answer 14

Dependable systems are crucial because they impact the well-being, safety, and welfare of individuals and society

Question 15

How do dependable systems prevent or minimize losses and damages?

Answer 15

They can prevent or minimize the losses or damages caused by system failures or malicious attacks

Question 16

What are the main activities in developing dependable systems?

Answer 16

Developing dependable systems involves activities such as considering sociotechnical systems, introducing redundancy and diversity, applying dependable processes, and using formal methods

Question 17

What factors influence dependability requirements?

Answer 17

Factors include the type and criticality of the system, the costs and benefits of dependability, and the expectations and needs of the stakeholders

Question 18

How can redundancy and diversity be achieved in systems?

Answer 18

Techniques include hardware redundancy, software redundancy, information redundancy, time redundancy, physical diversity, and logical diversity

Question 19

What are the advantages of using formal methods in system development?

Answer 19

Formal methods can improve system quality and dependability, support reuse and maintenance, and facilitate communication among stakeholders

Question 20

What are the disadvantages of using formal methods?

Question 21

What does dependability encompass in system attributes?

Answer 21

Dependability encompasses reliability, availability, safety, security, and maintainability

Question 22

What is the role of redundancy in dependability?

Answer 22

Redundancy involves introducing extra components or variants to cope with failures or attacks

Question 23

Explain how formal methods contribute to system development

Answer 23

Formal methods use rigorous mathematical techniques to specify, design, verify, and validate the system

Question 24

What challenges do sociotechnical systems pose for dependability engineering?

Answer 24

Sociotechnical systems challenge dependability engineering with complexity, diversity, uncertainty, emergence, and evolution

Question 25

Define availability in terms of dependability

Answer 25

Availability is the probability that a system will be operational and able to deliver the requested services at any point in time

Question 26

What is the primary goal of critical systems engineering?

Answer 26

The primary goal of critical systems engineering is to develop dependable critical systems that meet their requirements and standards

Question 27

What is the difference between safety-critical and business-critical systems?

Answer 27

Safety-critical systems involve the potential for harm to people or the environment, while business-critical systems are essential for an organization’s core operations

Question 28

What are some techniques for achieving redundancy in systems?

Answer 28

Techniques for achieving redundancy include hardware redundancy, software redundancy, information redundancy, time redundancy, physical diversity, and logical diversity

Question 29

How does redundancy contribute to dependability?

Answer 29

Redundancy provides backup or alternative functionality to cope with system failures or attacks, enhancing dependability

Question 30

What role do sociotechnical systems play in system development?

Answer 30

Sociotechnical systems consider interactions and dependencies between the software system and its social and organizational environment, recognizing their impact on dependability