critical systems intro
DESCRIPTION
Introduces the important topic of critical systemsTRANSCRIPT
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Critical systems video, 2013 Slide 1
Critical systems
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Critical system essentials
ReliabilityThe system must operate without serious failures
Availability The system must be available to deliver services when requested to do so
SafetyThe system should not harm people or the system’s environment
SecurityThe system must be able to protect itself and its data from malicious use
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Critical systems video, 2013 Slide 3
Critical system essentials
Safety
The system should not harm people or the system’s environment
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Critical systems video, 2013 Slide 4
Critical system essentials
Reliability
The system must operate without serious failures
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Critical systems video, 2013 Slide 5
Critical system essentials
Availability
The system must be available to deliver services when requested to do so
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Critical systems video, 2013 Slide 6
Critical system essentials
Security
The system must be able to protect itself and its data from malicious use
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Critical systems video, 2013 Slide 7
Dependability
ReliabilityThe system must operate without serious failures
Availability The system must be available to deliver services when requested to do so
SafetyThe system should not harm people or the system’s environment
SecurityThe system must be able to protect itself and its data from malicious use
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Critical systems video, 2013 Slide 8
Classes of critical system• Safety-critical systems
– Failure results in loss of life, injury or damage to the environment e.g. chemical plant protection system;
• Mission-critical systems– Failure results in failure of some
goal-directed activity e.g. spacecraft navigation system;
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Critical systems video, 2013 Slide 9
Classes of critical system• Business-critical systems
– Failure results in high economic losses e.g. customer accounting system in a bank;
• Infrastructure systems– Failure results in a loss of
infrastructure capability e.g. power distribution control system, broadband communications, etc.
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Critical systems video, 2013 Slide 10
Critical systems stack
Physical infrastructure
Infrastructure systemsSystem hardware
Operating system and middleware
External systemsCritical system X
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Critical systems video, 2013 Slide 11
Independent critical systems
• Infrastructure/hardware is part of the system
• System operation is not dependent on external systems
• Embedded control systems such as those in medical devices
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Critical systems video, 2013 Slide 12
Critical software systems• Usually rely on commodity
hardware/OS• System operation is dependent
on external infrastructure provision
• Hospital appointments system
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Systems of systems• A critical system is rarely a
single system but is a network of several software-intensive systems as well as infrastructure systems
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Systems of systems• Systems of systems (SoS) are
complex socio-technical systems with– Different owners and
management policies– Distributed operation– Heterogeneous hardware and
software
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Systems of systems• Individual systems may be part
of several SoS so– Conflicting requirements from
different uses of the system– Complex negotations may be
required when system changes are to be made
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Systems of systems• Systems that support
organisational needs (e.g. an inter-bank payments system) have to be designed to be robust so that they can cope with failures and unavailability in the other systems on which they depend
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Critical systems video, 2013 Slide 17
Summary• Critical systems are usually systems of
systems• Society depends on a range of critical
systems from control systems to infrastructure systems
• The more important characteristic of a critical system is its dependability, where dependability attributes are safety, reliability, availability and security
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Critical systems video, 2013 Slide 18
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