1. Mar.4.99 849 Dependable Embedded System -- Ying Shi Robustness

2. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -2 Outline Basic concepts Metric -- RB, major of this talk Metric -- RB, major of this talk other Robustness aspects + topic connections Conclusion Reference List Robustness Control Theory Manufacturing/ Quality QoS Exception Handling

3. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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

4. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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.

5. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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

6. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -6 Cover both HW & SW Both HW errors and SW errors to be covered traps 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.

7. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -7 Reality Restricts Ideally 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 reality 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.

8. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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... weighs quantitatively, how much of each metric weighs towards the final overall system robustness figure

9. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -9 More of Robustness Techniques towards Robustness –classical HW FTC techniques –graceful degradation –fail-safe –idiot-proof (UI) –functional diversity –etc...

10. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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

11. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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

12. Robustness - Dependable Embedded System Ying Shi Mar.4,99 -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