Software Availability and Safety: Concepts, Identification, and Analysis, Slides of Project Management

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Software availability

• Software availability

• the probability that a program is

operating according to requirements

at a given point in time.

• Availability = (MTTF/MTBF) x 100

Software Safety

• Software Safety is a software SQA

activity that focuses on identification of

potential hazards that may affect

software negatively and cause an entire

system to fail.

• Modeling and analysis process is

conducted as part of software safety.

• Hazards are identified and categorized

by criticality and risk.

• Once system-level hazards are identified, analysis techniques are used to assign severity, and probability of occurrence – similar to risk analysis
• To be effective, software must be analyzed in the context of the entire system
• Analysis techniques such as fault tree analysis can be used to predict the chain of events that can cause hazards and the probability that each of these events will occur to create the chain.
• Once hazards are identified and analyzed, safety- related requirements can be specified for the software. - For example, system can contain undesirable events and desired system responses to these events can be specified

Reliability versus Safety

• Closely related
• Software reliability uses statistical techniques to determine the likelihood that a software failure will occur
• Occurrence of a software failure does not necessarily result in a hazard or mishap
• Software safety examines the ways in which failures result in conditions that can lead to a mishap.

Characteristic of a Poka-yoke

device

• It is simple and cheap
• It is part of the process
• It is located near the process task

where the mistake occurs