Robustness

1. Robustness 849 Dependable Embedded System -- Ying Shi

2. Outline • Basic concepts • Metric -- RB , major of this talk • other Robustness aspects + topic connections • Conclusion • Reference List QoS Exception Handling Robustness Manufacturing/ Quality Control Theory Robustness - Dependable Embedded System

3. What’s Robustness • One of those system attributes such as performance • IEEE Standard Glossary • “The degree to which a system or component can function correctly in the presence of invalid inputs or stressful environmental conditions.” error tolerance, fault tolerance • specifically might be interpreted as the degree of the system ability of • handling exceptions • tolerating faults ... • One of the concerns -- establish Metric for this attribute Robustness - Dependable Embedded System

4. Robustness Benchmark (RB) • An identification of system error detection mechanism(EDM) • A RB should measure how a system reacts to possible erroneous inputs or environmental factors that could affect the system and result in failures. Robustness - Dependable Embedded System

5. System component Hierarchy • Robustness measure of a combined components system would provide an indication of how erroneous or unexpected inputs are handles by all levels of abstraction Robustness - Dependable Embedded System

6. Cover both HW & SW • Both HW errors and SW errors to be covered • Many HW EDMs are embedded in the design (CPU, mem, and I/O subsystems). Errors detected at this level, reflected to the SW level primarily through traps, almost always gracefully accommodated by the error handler (except crashes) • SW level, ideally, EDMs should be embedded within each of these levels to detect, isolate, and accommodate(via error handler)errors from coding or possibly design. Robustness - Dependable Embedded System

7. Reality Restricts • Ideally, to exercise all possible levels of error detection, trapped by both HW and SW, w/ the end result being a measurement w/ respect to an absolutely robust system • In reality, • exhaustive testing is not possible • natural errors occur infrequently enough that simply observing system operation is too time consuming. • Thus RB would serve as a relative measure of robustness or fault tolerance between two systems/machines. Robustness - Dependable Embedded System

8. Living with the Restriction • Try to cover more and make reasonable combining • Measure different system components:: • input error checking capability of system software • file system management • utilities • library routines ... • quantitatively, how much of each metric weighs towards the final overall system robustness figure Robustness - Dependable Embedded System

9. More of Robustness • Techniques towards Robustness • classical HW FTC techniques • graceful degradation • fail-safe • idiot-proof (UI) • functional diversity • etc... Robustness - Dependable Embedded System

10. Connections • Exception Handling • one of the means towards robustness • Control Theory • nah...leave with leo’s later talk • Quality of Service • robust system have the ability to guarantee QoS • they are two individual system attributes • Manufacturing/quality • robustness is the drive during manufacturing • robustness - one of system qualities Robustness - Dependable Embedded System

11. Conclusion • Robustness refers to one of the system attributes, also a goal in design • Complexity makes it impossible to have an ideal RB, thus as a relative metric b/w systems • RB as a guide for design • Robustness is quite a broad topic, I assume, there is too much to dig in the future to say any specific aspects of it are the main future trend Robustness - Dependable Embedded System

12. Reference List • Required paper :: Development of a Benchmark to Measure System Robustness, Siewiorek, Hudak, Suh, Segall, 23rd FTCS • insight into developing a system level RB • several primitive benchmarks, and combined into RB suites • a methodology to combine the primitive RBs to form an overall robustness figure • Journal • FTCS; R&M proceeding Robustness - Dependable Embedded System