Engineering the Quality Factors: Failure Severity Classes
Set of failures with same degrees of per-failure impact on users. Defined by experience with users/stakeholders/developers to:
- Compare similar products
- List factors considered as failure severity for the project
- Narrowing the list to most critical/measurable ones (some will be hard, i.e. impact on company reputation)
Conflicting viewpoints on severity classes should be addressed before the operational profile.
Classification Criteria include: cost, system-capability, human life, environment.
Cost-Based
Failure cost in terms of operation, repairs, business loss, disruption, etc.
System-Capability (services)
Loss of data, downtime, recoverability, etc.
Human-life based
Harmful to humans or environment, loss of human life, etc. Applicable to aeronautical, automotive, nuclear, health care industry, military systems, etc.
Environment Based
Harmful to environment, loss of wild-life, etc. Applicable to nuclear, chemical industry, etc.
| Severity Class | Cost Based Def ($) | System-Capability Impact | Human-life Based Def | Environment based Def |
|---|---|---|---|---|
| 1 | >100,000 | Basic service interruption (calls misforwarded or not forwarded) | possible loss of human life | severe and unrecoverable damage to environment/wildlife |
| 2 | 10,000 - 100,000 | Basic service degradation (phone # inoperable) | severe damage to human immune system/environment | Severe but partially recoverable damage to environment |
| 3 | 1,000 - 10,000 | Inconvenience, correction not deferrable (GUI for admins inoperable) | Minor damage to human immune system | Minor damage to Environment/wildlife |
| 4 | <1000 | Minor tolerable effects, correction deferrable (data missing from display) | Minor but recoverable deficiencies | Minor but recoverable deficiencies |