Lecture 1 - Overview Flashcards
• Critical systems have to be safe, available, reliable, secure and dependable • We have dierent classes of critical systems • Critical systems are socio-technical systems very much inuenced by the human factor in the development of such systems • Given the requirements of critical systems, critical systems engineering is more complex, and must accommodate for such requirements accordingly
What is a system (ICSE)
A system is a construct or collection of different elements that together
produce results not obtainable by the elements alone
What is Critical Systems Engineering
A field that focuses on the use of different methods and techniques to develop dependable and secure systems that are critical to a business, to safety, or to a particular mission.
What are Critical Systems
Systems where system failure typically leads directly to an incident that has an associated loss of some kind.
Name each type of Critical Systems
Safety Critical system
- Failure leads to loss of life, injury or damage to the environment
Mission Critical system
- Failure leads to failure of some goal directed activity
Business Critical System
- Failure leads to economic losses
Infrastructure Critical system
- Failure results in a loss of infrastructure capability
Name each critical System essentials
Safety
- the systems should not harm people or the systems environment
Availability
- The system must be available to deliver services when requested
Reliability
- The system must be able to protect itself and its data from malicious use
Resilience
- The ability to resist and recover from damaging events
What is meant by Critical Systems Stack
Critical Systems are generally connected together with multiple systems in order to produce a goal.
Critical Systems have to take into consideration all elements in the stack to ensure that the Critical System is dependable.
hardware Failure
Network Failure
Infrastructure Failure
OS failure
Name two types of Critical system Dependencies
Independent Critical systems
- These are embedded control systems in which its system operation is not dependent on external systems.
Infrastructure/hardware is part of the system
Not connected to other systems, thus we can analyse the whole system independently.
Critical Software systems
- These are Software Systems in which system operation is dependent on external infrastructure provision.
Usually they are reliant on its commodity hardware/OS
Dependent on external systems
What are System of Systems (SoS)
A critical system is rarely a single system but is a network of several
software-intensive systems as well as infrastructure systems
These systems typically work together to achieve a goal (service), and thus will have to be designed to be robust so that they can cope with failures and unavailability in other systems on which they depend on.
Why are System of systems referred to as Socio-technical Systems
System of Systems are complex socio-technical systems that have various systems with:
- Different owners and management policies
- Distributed operation
- Heterogeneous (Diverse/various) hardware and software
Individual Systems may be part of several SoSs, thus they can be Conflicting requirements from different uses of the system, and Complex negotiations may be required when system changes are to be made.
what do Socio-Technical systems include (Summary)
- IT systems and the social and organisational environment in which these systems are used
- Key infuences are human behaviour, organisational processes and policies, regulations, culture
What is regulation?
Regulators are government-appointed bodies whose job is to ensure that companies and
other bodies conform to national and international laws.
Regulators interpret the law and government policy and establish standards and
regulations that must be followed by industry.
Examples of regulators
* Information Commissioner’s Office (Data protection authority)
* Civil Aviation Authority (CAA)
* Bank of England
* Office of Gas and Electricity Markets (Ofgem) – electricity and gas generator regulator
* Medicine and Healthcare Products Regulatory Agency (MHRA)
Why are Regulators involved in Critical Systems
Some critical systems may have to be certified by regulators before they are put into use.
This is particularly true for safety-critical systems.
The regulators check that the system conforms to current regulations and standards
- Usually have to produce evidence that demonstrates that the system is dependable.
Name two levels of Critical Systems
Primary Critical Systems
- Systems in which system failure typically leads directly to an incident that has an associated loss of some kind.
- Typically, these are control systems or systems that are closely associated with control systems
- Example – failure of a car engine management system causes the engine to cut out while
driving
Secondary Critical Systems
- Systems whose failure may (but need not) lead to failure in an associated system that then
leads to loss of some kind
- Example – medical information system that maintains incorrect information about treatments
Why is Critical System Engineering so Important
The cost of critical system failure is so high that development methods
may be used that are not cost-effective for other types of system.
An important aim for many critical systems is certification and the
development process has to be geared to achieving such certification.
How is Software Engineering used to develop critical systems
Formal methods for systems specification and analysis.
* Use of specialised tools e.g. model checkers and static analysers.
* Risk-driven approach to system specification and management.
* Argumentation systems to support the development of dependability cases.
* Disciplined configuration management of all software and hardware.
* Detailed process record keeping.
