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Things Structural Clones Tell that Simple Clones Don’t

Things Structural Clones Tell that Simple Clones Don’t. Hamid Abdul Basit. Software Clones. Simple clones the same or similar code fragments Structural clones higher-level , larger similarities Similarity of code and similarity of structure. Simple clones. Structural Clones.

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Things Structural Clones Tell that Simple Clones Don’t

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  1. Things Structural Clones Tell that Simple Clones Don’t Hamid Abdul Basit

  2. Software Clones • Simple clones • the same or similar code fragments • Structural clones • higher-level, larger similarities • Similarity of code and similarity of structure

  3. Simple clones

  4. Structural Clones

  5. Structural Clones CreateTask CreateProject CreateTask.UI CreateTask() CreateProject.UI CreateProject() User Interface executes executes CreateTask.BL ValidateTask() CreateProject.BL ValidateProject() Business Logic visualizes visualizes accesses accesses Task.DB AddTask() Task Table Project.DB AddProject() Project Table Database Collaborative structural clone

  6. When are structural clones useful? • showing a bigger picture of similarity situation - the forest from the trees • Finding refactoring opportunities • Architecture recovery, program understanding and maintenance • Structural clones often represent application domain or design concepts • Re-engineering for reuse • The bigger the clones the better for reuse • Some benefits for plagiarism detection

  7. A x y C B z w D A structure is a graph • Entities {A,B,C,D} • Relationships {w,x,y,z}

  8. Entities • Physically defined • Code fragments, files , web pages, directories • Semantically defined • Methods, classes, packages • Conceptually defined • Components, sub-systems

  9. Relationships • Physical co-location • Same file, same directory • Runtime • Message passing • Hyperlink between web pages • Design level • Inheritance • Association • Composition

  10. Structural Clones S6 S5 S4 e6a e5a e4a y y y y y x e6b x e6d e5b x e5d e4b e4d z z z e6c e5c e4c S8 S7 e8a e7a w y y y x e8b x e7b e8d e7d z z e8c e7c

  11. Observation Higher level similarities are composed of lower level similarities Can be recovered by finding repeating configurations of lower level similarities

  12. Detecting Structural Clones clone patterns Simple clones in files 2 3 4 5 1 1,4,8,10,11,12 6 7 8 9 10 1,4,7,8,10,11,12 13 11 12 14 15 2,5,9,13,15

  13. Detecting Structural Clones File Analysis 7 13 5 12 8 4 15 11 10 9 2 1

  14. 7 13 5 12 8 4 15 11 10 9 2 1 Detecting Structural Clones Directory Analysis

  15. Detecting Structural Clones File Level Structural Clone Across Directories 1 4 8 10 7 2 9 13 15 5

  16. Simple Clone Structure (SCS)Across Files a2 a1 b1 b2 c2 c1 F1 F2

  17. File Clone Class (FCC) F1 F2

  18. File Clone Structure (FCS) Across / Within Directories F1 Y1 Y2 F2 X1 Z1 Z2 X2 D2 D1

  19. In earlier work • We hypothesized the benefits of structural clones • Re-engineering for reuse, architecture recovery, … • Defined structural clones • Implemented Clone Miner – structural clone detector • Did initial empirical evaluation

  20. In work presented here How frequent are the different types of structural clones? Are structural clones more meaningful for program understanding and design recovery than simple clones? What is the value added by structural clone detection in identifying refactoring opportunities?

  21. Case Study Systems

  22. Systems’ Overview

  23. Simple Clone Classes (SCC)

  24. % Methods Containing SCC

  25. How frequent are the different types of structural clones? 1

  26. Structural Clones are Frequent • Simple clones tend to occur in groups • 56% of simple clones are within structural clones • There are less structural clones than simple clones

  27. Simple Clone Classes (SCC) and Simple Clone Structures (SCS)

  28. Simple Clone Structures (SCS)Across Files

  29. % SCC Covered By SCS Across Files

  30. Simple Clone Structures (SCS)Within Files

  31. % Files Containing SCS Within Files

  32. Simple Clone Structures (SCS) Across Methods

  33. % SCC Covered By SCS Across Methods

  34. Method Clone Classes (MCC) and Method Clone Structures (MCS)

  35. Method Clone Classes (MCC)

  36. Method Clone Structures (MCS) Across Files

  37. File Clone Classes (FCC) and File Clone Structures (FCS)

  38. File Clone Classes (FCC)

  39. File Clone Structures (FCS)Across Directories

  40. File Clone Structures (FCS)Within Directories

  41. Are structural clones more meaningful for program understanding and design recovery than simple clones? 2

  42. Improved Program Understanding and Design Recovery • Analysis is more qualitative than quantitative • anecdotal evidences of interesting examples of various types of structural clones • Larger program parts recovered as clones from a system are expected to be more meaningful than smaller ones • High level structural clones like FCC and FCS appear to be a very useful tool for design recovery because of their size, highlighting the design level similarities between various parts of the system

  43. FCC Examples from Apache-Ant

  44. FCC examples from FreeCol

  45. FCC examples from DrJava

  46. FCC examples from JFreeChart

  47. FCC Example from Javax-Swing

  48. FCC Example from Javax-Swing

  49. FCS Example from JFreeChart

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