Dependable Systems Flashcards
1
Q
Most important aspect of many systems
A
- Dependability of the system
2
Q
Dependable system
A
- Reliability
- Availability
- Security
3
Q
Hardware failure
A
- Hardware fails because of design and manufacturing errors, or because components have reached the end of their natural life.
4
Q
Software failure
A
- Software fails due to errors in its specification, design, or implementation.
5
Q
Operational failure
A
- Human operators make mistakes. This is now perhaps the largest single cause of system failures in sociotechnical systems.
6
Q
Redundancy
A
- The inclusion of spare capacity in a system that can be used in the event of failure of part of the system
7
Q
Diversity
A
- The use of different types of redundant components so that the probability of a common failure that affects all redundant components is reduced
8
Q
Formal methods
A
- Formal specification
- Specification analysis and proof
- Transformational development
- Program verification
9
Q
Verification-based approaches
A
- These are different representations of a software system such that a specification and a program implementing that specification are proved to be equivalent.
- This demonstrates the absence of implementation errors.
10
Q
Refinement-based approaches
A
- A representation of a system is systematically transformed into another, lower-level representation, e.g., a specification is transformed automatically into an implementation.
- This means that, if the transformation is correct, the representations are equivalent.
11
Q
Causes of failures
A
- Hardware
- Software
- Operational failure
12
Q
Dependability costs:
A
- Increase exponentially with dependability requirement.
13
Q
Holistic system design
A
- Interaction between all components and layers in a system
14
Q
Dependability process
A
- Explicitly defined
- Repeatable
15
Q
Formal methods
A
- Approaches to software development based on mathematical representation and analysis
