L10 - Dependability Flashcards
Fault Types
- time (transient, permanent, intermittent)
- internal (physical, design)
- external (physical, input data)
Heisenbugs
software bug that seems to disappear or alter its behavior when one attempts to study it
Fault Tolerance enables _________________. It requires ___________ and prior _____________.
Fault Tolerance enables the system to work in presence of faults. It requires fault detection and prior error specification.
Which exceptions can be detected by the environment?
- synchronously raised exceptions (divide by zero)
- asynchronously raised exceptions (failure of health monitoring mechanism)
Exceptions detected by application
- Synchronously raised (failure of a program check)
- asynchronously raised exceptions (process recognises error that leads to missing deadline)
Error
wrong state in system
Transient Fault
A transient fault starts at a particular time and remains in the system until it disappears.
A permanent fault _______________ until _______________.
A permanent fault remains in the system until repaired.
Intermittent Fault
An intermittent fault is defined as a transient fault that occurs sporadic from time to time.
Impairments
Faults, Errors and Failures.
Name three key requirements for attributes.
- Availability (Readiness for Usage)
- Reliability (Continuity of Service Delivery)
- Safety (Non-Occurence Of Catastrophic Consequences)
- Confidentiality (Non-Occurence of unauthorized disclosure)
- Integrity (Non-Occurence of improper alteration of information)
- Maintainability (Aptitude to undergo repairs or evolutions)
Confidentiality
Confidentiality is the non-occurence of unauthorized disclosure.
A test only shows _____________ of faults not their _____________.
A test only shows presence of faults not their absence.
What activates an exception handler and with what is it associated with?
An exception handler gets activated with an exception and associated with a domain that specifies a region of computation. There may be several handlers for a particular exception.
Decomposition is also known as ____________. How is it defined?
Decomposition is also known as Top Down Design. It is defined as the systematic breakdown of complex into smaller system. Isolated components can be understood and engineered as individuals.
What is an alternative description of abstraction and whats the concept behind?
Abstraction (Bottom Up Design): detailed consideration of components.
What is described by information hiding and how do you implement it in C?
Information hiding is the reduced visibility outside of the module. In C: .h-file contains an interface of module, .c-file contains body - no formal relationship.
Name characteristics of Ada.
- planned to be mandatory for all DoD projects that include embedded systems
- latest version is Ada 2012^ block-structured language
- constructs control how tasks are dispatched
- consists out of subprogram/package/task/protected unit
What is a disadvantage of C?
C does not provide native exception handling. This has to be implemented by the programmer.
C is a _________________ and therefore provides _________________ without _________________.
C is a low level programming language and therefore provides structure and flexibility without complex language restrictions.
Name an advantage and a problem that occurs while developing RTS in C++.
- Better software engineering practice because of encapsulation and more advanced level of abstraction as in C
- Lack of concurrent software with predictable timing behaviour makes it difficult to develop software for RTS.
