19.4 Safety-Critical Products

Several classifications regarding criticality apply to software products. Table 19-1 shows an example.

Table 19-1. Safety Criticality Classification Example

	Level (Weight)
Type	A (100,000,000)	B (100,000)	C (100)	D (1)
Safety	Many people killed	Human lives in danger	Damage to physical objects; risk of personal injury	Insignificant damage to physical objects; no risk to human beings
Economy	Financial catastrophe (the company must close)	Great financial loss (the company is threatened)	Significant financial loss (the company is affected)	Insignificant financial loss
Security	Destruction/disclosure of strategic data and services	Destruction/disclosure of critical data and services	Errors in data	No risk for data
Environment	Comprehensive and irreparable damage to the environment	Reparable, but comprehensive damage to the environment	Local damage to the environment	No environmental risk

Examples

At level A are found systems for air traffic control and military systems. At level B are found fire-fighting systems and integrated financial systems. At level C are found fire alarms and financial systems in isolation. At level D are found office automation systems and entertainment systems. A system may of course be of different levels for different types of risks. The combined weight determines the final classification.

Configuration Management Considerations

There are no unambiguous rules for the kind of configuration management that must be performed as a result of a product's criticality level, but the need for formality and automation increases with the level of criticality. For the majority of products on levels A and B, standards apply that include requirements for configuration management. For this reason, it's practical to follow the standards (see Chapter 3).