1. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Evaluating Key Statements Analysis David Binkley - Loyola College, USA Nicolas Gold, Mark Harman, Zheng Li, Kiarash Mahdavi CREST, King’s College London, UK

2. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Overview KSA Two metrics –Impact –Cohesion Research Questions Empirical study Results

3. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Key Statement Analysis (KSA) Identify key statements The statements that capture most impact with highest cohesion

4. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Why KSA Many analyses produce far too much e.g. slicing, chopping

5. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Framework Modules Functions Classes Concept bindings Principal Variables Key Statements

6. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Principal Variables (PV) Bieman and Ott’s Principal Variables PV G – a global variable assigned in F PV O – a variable used in an output statement in F PV G U PV O

7. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li void cylinder(int r, h) { D=2*r; perimeter=PI*D; undersurface=PI*r*r; sidesurface=perimeter*h; area=2*undersurface+sidesurface; volume=undersurface*h; printf(“\nThe Area is %d\n", ); printf(“\nThe Volume is %d\n", ); } r h area volume

8. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Metrics for KSA Impact: outward influence of the key statements Cohesion: inward connectedness of the key statements

9. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Cohesion

10. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Dependence Cluster

11. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li The worst case for KSA If all statements in a module are in a dependence cluster…

12. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Research Questions Size Impact Cohesion Large dependence cluster

13. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Analysis Subjects

14. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Tools CodeSurfer SPSS

15. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Impact

16. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Cohesion

17. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li Results Size –25% of the function size Impact –70% of impact of the function. Cohesion –More than 80% of cohesion Large Dependence Cluster –a clear and largely negative impact

18. SCAM’08 -- Evaluating Key Statements AnalysisZheng Li less is more