ch9 - Critical Systems Specification Ian Sommerville 2004...

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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 1 Critical Systems Specification
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 2 Objectives To explain how dependability requirements may be identified by analysing the risks faced by critical systems To explain how safety requirements are generated from the system risk analysis To explain the derivation of security requirements To describe metrics used for reliability specification
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 3 Topics covered Risk-driven specification Safety specification Security specification Software reliability specification
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 4 Dependability requirements Functional requirements to define error checking and recovery facilities and protection against system failures. Non-functional requirements defining the required reliability and availability of the system. Excluding requirements that define states and conditions that must not arise.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 5 Risk-driven specification Critical systems specification should be risk- driven. This approach has been widely used in safety and security-critical systems. The aim of the specification process should be to understand the risks (safety, security, etc.) faced by the system and to define requirements that reduce these risks.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 6 Stages of risk-based analysis Risk identification Identify potential risks that may arise. Risk analysis and classification Assess the seriousness of each risk. Risk decomposition Decompose risks to discover their potential root causes. Risk reduction assessment Define how each risk must be taken into eliminated or reduced when the system is designed.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 7 Risk-driven specification
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 8 Risk identification Identify the risks faced by the critical system. In safety-critical systems, the risks are the hazards that can lead to accidents. In security-critical systems, the risks are the potential attacks on the system. In risk identification, you should identify risk classes and position risks in these classes Service failure; Electrical risks;
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 9 Slide 9 Insulin pump risks Insulin overdose (service failure). Insulin underdose (service failure). Power failure due to exhausted battery (electrical).
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This note was uploaded on 10/01/2010 for the course CS 1292 taught by Professor Aabdollah during the Spring '10 term at NJ City.

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ch9 - Critical Systems Specification Ian Sommerville 2004...

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