Dependability

1
Dependability

• Availability
• How likely that system will be up and running?

• Reliability
• How likely that system behaves correctly?

• Safety
• How likely is system to cause damage?

• Security
• How likely can system defend against accidental
  or deliberate intrusion?

2
Improving Dependability

• Avoidance
• Conservative (programming) conventions to prevent
  introduction
• Detection and Removal
• Testing and debugging
• Limitation of Influence (fault tolerance)
• Designing system to recover gracefully from
  failures at runtime

3
Verification Validation

• Verification (Are we building the product
  right?)
• Defect Testing
• Static inspections
• code reviews
• automatic static analysis
• Dynamic inspections
• component and integration testing
• regression testing
• Statistical Testing

4
Verification Validation Defect Testing

• Code Reviews
• line-by-line public study of code
• catches potential bugs, not necessarily program
  faults
• Enforces adherence to Coding Standards
• Coding Standards
• Development-team-wide conventions for source code
  and programming style

5
Verification Validation Defect Testing

• Component Testing
• Black-box
• Equivalence Partitioning
• White-box
• Path Coverage (program flow graphs)

6
Verification Validation Defect Testing

• Integration Testing
• Top-down
• stubs
• Bottom-up
• testing harnesses
• Stress testing
• shotgun testing

7
Verification Validation

• Validation
• not really discussed explicitly
• Acceptance-testing
• alpha testing
• trial run for bespoken client
• beta testing
• usually prior to sale (or reduced price), but
  less personal