I used this set of slides for a talk I gave at the Qualimetrie Club, Paris on June 2009.

1. what history can tell us
Tudor Gîrba
www.tudorgirba.com

2. 2002

3. PhD
2002 2005

4. PhD PostDoc
2002 2005 2009

5. PhD PostDoc
2002 2005 2009
Consultant
eng.ch
w ww.sw-

6. {
{
}
}
{
{
}
}
for
wa
rd
en
gin
eer
ing

7. ing
eer
gin
en
rd
wa
for
{ {
{ { {
{
{ { }
} } actual development }
}
} } } { }

8. ing
eer
rev
gin
ers
en
ee
rd
ng
wa
ine
for
eri
ng
{ {
{ { {
{
{ { }
} } actual development }
}
} } } { }

9. e.uni be.ch
m oos

10. 03
ucasse 20
Lanza, D

11. {
{
}
}
{
{
}
}
for
wa
rd
en
gin
eer
ing
actual development
er ing
g ine
e en
ev ers
r
{
{
}}
}
{
{
{
}
}

12. {
{
}
}
{
{
}
}
for
wa
rd
en
gin
eer
ing
reverse engineering
actual development
er ing
g ine
e en
ev ers
r
{
{
}}
}
{
{
{
}
}

13. 001
Lehma n etal, 2

14. commit
time
Wu etal
,2 004

15. Evolution Matrix shows changes in classes
Idle class
Pulsar class
Supernova class
White dwarf class
2002
ucasse,
Lanza, D

16. 2002
ucasse,
Lanza, D

18. eta-model?
h at is the m
w

19. { {
{ {
}
}
}
} { }
complex, large
{
{
{
{

20. { { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }

21. eta-model?
h at is the m
w

22. Modeling History
to Understand Software Evolution
Inauguraldissertation der
Philosophisch-naturwissenschaftlichen
Fakultät der Universität Bern
vorgelegt von
Tudor Gîrba
von Rumänien
Leiter der Arbeit:
Prof. Dr. Stéphane Ducasse
Prof. Dr. Oscar Nierstrasz
Institut für Informatik und
angewandte Mathematik

23. Idle
class
Pulsar
class
Supernova
class
White dwarf attributes
class
methods Class

24. Idle
class
Pulsar
class
Supernova
class
White dwarf attributes
class
methods Class

25. Idle
class history
Pulsar
class history
Supernova
class history
White dwarf ClassHistory
class history
isPulsar
isIdle

26. System
Version
Class
Version

27. System
Version
Class Class
History Version

28. System System
History Version
Class Class
History Version

29. System System
History Version
Class Class
History Version

30. History Version
History Version

31. ry exp licitl0y5
dels h isto 0
Girba 2
H ismo mo
History Version
History Version

32. what changed? when, how?
2 4 3 5 7
2 2 3 4 9
2 2 1 2 3
2 2 2 2 2
1 5 3 4 4

33. Evolution of
LENOM(C) = ∑ |NOMi(C)-NOMi-1(C)| 2i-n
Number of Methods
LENOM(C) = 4 + 2 + 1 + 0 = 7
1 5 3 4 4
4
Gîrba etal 200

34. Latest Evolution of
LENOM(C) = ∑ |NOMi(C)-NOMi-1(C)| 2i-n
Number of Methods
Earliest Evolution of
EENOM(C) = ∑ |NOMi(C)-NOMi-1(C)| 22-i
Number of Methods
LENOM(C) = 4 2-3 + 2 2-2 + 1 2-1 + 0 20 = 1.5
1 5 3 4 4
EENOM(C) = 4 20 + 2 2-1 + 1 2-2 + 0 2-3 = 5.25
4
Gîrba etal 200

35. ENOM LENOM EENOM
2 4 3 5 7 7 3.5 3.25
2 2 3 4 9 7 5.75 1.37
2 2 1 2 3 3 1 2
2 2 2 2 2 0 0 0
1 5 3 4 4 7 1.25 5.25

36. ENOM LENOM EENOM
balanced changer 7 3.5 3.25
late changer 7 5.75 1.37
3 1 2
dead stable 0 0 0
early changer 7 1.25 5.25

37. mea suredENOM
ry ca n be LENOM EENOM
Histo
balanced changer 7 3.5 3.25
late changer 7 5.75 1.37
3 1 2
dead stable 0 0 0
early changer 7 1.25 5.25

38. Evolution Number of Methods
Stability Number of Lines of Code
Historical Max of Cyclomatic Complexity
Growth Trend Number of Modules
... ...

39. common wisdom: recently changed parts are likely to
change in the near future

40. common wisdom: recently changed parts are likely to
change in the near future
r eally?

41. 30% 90%

44. present

45. past
present

46. past future
present

47. past future
present

48. past future
present

49. past future
prediction hit present

50. past future
YesterdayWeatherHit(present):
past:=histories.topLENOM(start, present)
future:=histories.topEENOM(present, end)
past.intersectWith(future).notEmpty()
prediction hit present

51. Yesterday’s Weather shows the localization of
change
hit hit hit
YW = 3 / 8 = 37%
hit hit hit hit hit hit hit
YW = 7 / 8 = 87%
04
Girba etal, 20

52. Detection Strategies
are metric-based queries
to detect design flaws

53. God Class:
class.ATFD() > FEW &
class.WMC() >= VERY HIGH &
class.TCC() < ONE THIRD

54. God Class:
class.ATFD() > FEW &
class.WMC() >= VERY HIGH &
class.TCC() < ONE THIRD
f it is s table?
what i

55. Harmless God Class:
classhistory.last.isGodClass() &
classhistory.STABILITY(NOM) >= VERY HIGH
2004
Rat iu etal,

56. A A A A A
B C B C B C B B
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5

57. A A A A A A A A A A A A A A A A A A A A
B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B
D D D E D D D E D D D E D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A A A A A A A A A A A A A A A A
B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B
D D D E D D D E D D D E D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A A A A A A A A A A A A A A A A
B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B
D D D E D D D E D D D E D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A A A A A A A A A A A A A A A A A A A A
B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B
D D D E D D D E D D D E D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5

58. System System
History Version
Class Class
History Version

59. System System
History Version
Inheritance
Version
Class Class
History Version

60. System System
History Version
Inheritance Inheritance
History Version
Class Class
History Version

61. A A A A A
B C B C B C B B
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
A is persistent, B is stable, C was removed, E is newborn ...

62. A
A A A A A
B C B C B C B B
C B
D D D E
ver .1 ver. 2 ver. 3 ver. 4 ver. 5
D E
A is persistent, B is stable, C was removed, E is newborn ...
05
Girba etal, 20

63. Hierarchy Evolution reveals evolution patterns
05
Girba etal, 20

64. 1 2 3 4 5 6
A
A
B
B E
C
D
E C D
99 8
Ga ll etal, 1

65. 1 2 3 4 5 6
A
B
C
D
Version
E

66. 1 2 3 4 5 6
A
B
C
D
Version
E changed

67. 1 2 3 4 5 6
A History
changed(i)
B
C
D
Version
E changed

68. 1 2 3 4 5 6
A
B
C
D
E

69. {A, B, C, D, E}
1 2 3 4 5 6 Ø
A {A, D, B} {A, E, C, D}
{2} {6}
B
{D, B} {A, D} {A, E, C}
C FCA
{2, 4} {2, 6} {5, 6}
D
{D} {A} {C}
E {2, 4, 6} {2, 5, 6} {3, 5, 6}
Ø
{1, 2, 3, 4, 5, 6}

70. {A, B, C, D, E}
1 2 3 4 5 6 Ø
A {A, D, B} {A, E, C, D}
{2} {6}
B
{D, B} {A, D} {A, E, C}
C FCA
{2, 4} {2, 6} {5, 6}
D
{D} {A} {C}
E {2, 4, 6} {2, 5, 6} {3, 5, 6}
Ø
{1, 2, 3, 4, 5, 6}
0 7
Girba etal, 20

71. Parallel Inheritance
add simultaneously children to several classes
Shotgun Surgery
change several classes simultaneously, but do not add methods

72. {
{
}
}
{
{
}
}
for
wa
rd
en
gin
eer
ing
reverse engineering
actual development
n g
e eri
n gin
rs ee
r eve
{
{
}}
}
{
{
{
}
}

73. Tudor Gîrba
www.tudorgirba.com
creativecommons.org/licenses/by/3.0/