1. NASA Software Assurance Symposium 2001 Metrics for Fault-Tolerant Real-Time Software Afzel Noore Computer Science and Electrical Engineering West Virginia University September 6, 2001

2. NASA Software Assurance Symposium 2001Outline Literature Review and Background Literature Review and Background Extension of Function Point Metrics Extension of Function Point Metrics Software Fault-Tolerant Structures Software Fault-Tolerant Structures Proposed Metrics Framework Proposed Metrics Framework Summary Summary Future Work Future Work

3. NASA Software Assurance Symposium 2001 Why Function Point Metrics? Language independent Provides better design visibility Useful as an estimation technique Used as a measure of productivity Helpful in managing change of scope

4. NASA Software Assurance Symposium 2001 Function Point Applications Function Point Applications Prediction of the maintenance efforts Measurement of size and complexity of algorithms Sizing and costing individual components of software Useful for checking requirements completeness

5. NASA Software Assurance Symposium 2001 Function Point Calculation Function Point Calculation Identification of the subsystem boundaries Identification of data functions EIF (External Interface Files) ILF (Internal Logical Files) Identification of transactional functions EI (External Input) EO (External output) EQ (External Enquiry) Calculation of Unadjusted Function Point Count UFPC = ΣEI*w + ΣEO*w + ΣEQ*w + ΣILF*w + ΣEIF*w (w is the corresponding weight assigned)

6. NASA Software Assurance Symposium 2001 Function Point Calculation... Function Point Calculation... Determination of the Value Adjustment Factor VAF = (TDI * 0.01) +0.65 TDI is the Total Degree of Influence Calculation of the Adjusted Function Point Count) AFPC = VAF * UFPC

7. NASA Software Assurance Symposium 2001 Limitations of Function Point Analysis Limitations of Function Point Analysis Does not provide accurate measures for real-time software The number of sub-processes in a real-time software varies continuously There are a large number of single-occurrence control variables, which can not be counted by FPA

8. NASA Software Assurance Symposium 2001 Full Function Point and COSMIC Full Function Point and COSMIC In 1997, St-Pierre proposed the Full Function Points approach as an extension to the IFPUG standard to capture the functional size of real-time applications. Common Software Measurement International Consortium (COSMIC) Full Function Point The COSMIC initiative draws an international team of software metrics experts to establish principles of the new measurement method based on the best features of existing IFPUG, Mark II, and FFP methods.

9. NASA Software Assurance Symposium 2001 Evolution of Function Point Metrics FPA FPA 3.4FPA 4.0FPA 4.1 FPA Albrecht 79 IFPUG 90IFPUG 94IFPUG 99Albrecht 84 Mark II FPAMark II FPA 1.3.1 Symons 88UKSMA 98 St-Pierre 97 FFP1.0 FFP2.0FFP2.1 COSMIC 99, 2001

10. NASA Software Assurance Symposium 2001 Extension for RT & FT Software Extension for RT & FT Software FPA FPA 3.4FPA 4.0FPA 4.1 FPA Albrecht 79 IFPUG 90IFPUG 94IFPUG 99Albrecht 84 Mark II FPAMark II FPA 1.3.1 Symons 88UKSMA 98 St-Pierre 97 FFP1.0 FFP2.0FFP2.1 COSMIC 99, 2001

11. NASA Software Assurance Symposium 2001 Extension for RT & FT Software Extension for RT & FT Software IFPUG FPACOSMIC FFP EFP

12. NASA Software Assurance Symposium 2001 Management Process – FPA EI : External Input EO: External Output EQ: External Inquiry ILF: Internal Logical File EIF: External Interface File Design or Selection of Metamodel Design or Selection of Metamodel Control Process – FFP ECE: External Control Entry ECX: External Control Exit ICR : Internal Control Read ICW: Internal Control Write RCG: Read-only Control Group UCG: Updated Control Group

13. NASA Software Assurance Symposium 2001 Control Implementation – EFP CIS: Control Implementation Structure RDS: Redundant Data Sets RA: Redundant Algorithms AC: Algorithmic Complexity VSA: Version Sequential Arrangement TC: Timing Constraints Design or Selection of Metamodel...

14. NASA Software Assurance Symposium 2001 Characterization of Software Characterization of Software Control Implementation Structure RB: Recovery Block NVP: N-Version Programming CRB: Consensus Recovery Block DRB: Distributed Recovery Block EDRB: Extended Distributed Recovery Block RFCS: Roll-Forward CheckPointing Scheme NSCP: N Self-Checking Programming NCP: N-Copy Programming RTB: Retry Block

15. NASA Software Assurance Symposium 2001 Req.100: 1 1 1 1 FA FB FC FD Req.86 1 EXTERNAL CONTROL EXIT Req.79Req.37Req.35Req.38 SP1 SP2 EXTERNALCONTROLENTRYEXTERNALCONTROLENTRY LA LB LC Req.100: 1 1 1 Req.87 1 Req.79 Trip 1 F: Power Flux A,B,C,D. SP: High Power Flux Set-Point Algorithm: 2 out of 4 Power Flux (FA,FB,FC,FD) must be greater than High Power Flux Set-Point (SP2). Nuclear Reactor

16. NASA Software Assurance Symposium 2001 Recovery Block - Design Diversity Recovery Block - Design Diversity

17. NASA Software Assurance Symposium 2001 Recovery Block - Software Structure Recovery Block - Software Structure BEGIN ENSURE acceptance test; BY Primary alternative; ELSE IF NOT THEN BY 2nd alternative; ELSE error; FI ELSE IF NOT THEN BY 3rd alternative; ELSE error; FI

18. NASA Software Assurance Symposium 2001 Recovery Block - Software Structure... Recovery Block - Software Structure... …… ELSE IF NOT THEN BY n ’ th alternative; ELSE error; FI ELSE Error; END Structural Complexity: O(n)

19. NASA Software Assurance Symposium 2001 Recovery Block - Design Diversity Recovery Block - Design Diversity CIS: Control Implementation Structure RDS: Redundant Data Sets RA: Redundant Algorithms AC: Algorithmic Complexity VSA: Version Sequential Arrangement TC: Timing Constraints Recovery Block AverageHighHighHighHigh

20. NASA Software Assurance Symposium 2001 N Copy Programming - Data Diversity N Copy Programming - Data Diversity

21. NASA Software Assurance Symposium 2001 N Copy Programming - Data Diversity N Copy Programming - Data Diversity CIS: Control Implementation Structure RDS: Redundant Data Sets RA: Redundant Algorithms AC: Algorithmic Complexity VSA: Version Sequential Arrangement TC: Timing ConstraintsNCP High N / A Average

22. NASA Software Assurance Symposium 2001 Retry Block - Data Diversity Retry Block - Data Diversity

23. NASA Software Assurance Symposium 2001 Retry Block - Data Diversity Retry Block - Data Diversity CIS: Control Implementation Structure RDS: Redundant Data Sets RA: Redundant Algorithms AC: Algorithmic Complexity VSA: Version Sequential Arrangement TC: Timing Constraints Retry Block High N / A Average High

24. NASA Software Assurance Symposium 2001 Numerical Assignments Numerical Assignments

25. NASA Software Assurance Symposium 2001 Numerical Assignments …. Numerical Assignments ….

26. NASA Software Assurance Symposium 2001 Function Point Calculations …. Function Point Calculations …. Definition of numerical assignment rules CIS = RDS + RA + AC + VSA + TC 1.The lowest CIS * Percentage > 1 in both category. 2.The lowest CIS * Percentage (Design Diversity) > the highest CIS * Percentage (Data Diversity) CIS Factor = (RDS + RA + AC + VSA + TC) * Diversity Percentage 30% for Diversity Percentage in Design Diversity Category 22% for Diversity Percentage in Data Diversity Category EFP = Management FP + Control FP * CIS Factor

27. NASA Software Assurance Symposium 2001 Extended Metrics Characteristics Extended Metrics Characteristics

28. NASA Software Assurance Symposium 2001 Extended Metrics Characteristics …. Extended Metrics Characteristics ….

29. NASA Software Assurance Symposium 2001 Extended Metrics Characteristics …. Extended Metrics Characteristics ….

30. NASA Software Assurance Symposium 2001 Sub-process Representation of Requirements Representation of Requirements Functional users requirements Functional processes Data movement type Data transform type and Software

31. NASA Software Assurance Symposium 2001 Factors for Extended Metrics Framework Factors for Extended Metrics Framework Structural complexity Functional size Fault tolerant requirements Algorithm complexity Algorithm implementation Reused-algorithms Connectivity Effort

32. NASA Software Assurance Symposium 2001 Summary and Future Work By augmenting new elements based on FFP and FPA techniques, a new Extensive Function Point composite metrics has been proposed for software with real-time and fault-tolerant attributes. Future work will focus on data collection and validation of the proposed metrics framework.