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

2002

PhD
2002 2005

PhD PostDoc
2002 2005 2009

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

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

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

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

e.uni be.ch
m oos

03
ucasse 20
Lanza, D

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

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

001
Lehma n etal, 2

commit
time
Wu etal
,2 004

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

2002
ucasse,
Lanza, D

eta-model?
h at is the m
w

{ {
{ {
}
}
}
} { }
complex, large
{
{
{
{

{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }
{ { { { { { { { { { { {
{ { { { { { { { { { { {
} } } } } }
}
} }
} }
} }
} }
} }
}
} { } } { } } { } } { } } { } } { }

eta-model?
h at is the m
w

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

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

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

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

System
Version
Class
Version

System
Version
Class Class
History Version

System System
History Version
Class Class
History Version

System System
History Version
Class Class
History Version

History Version
History Version

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

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

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

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

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

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

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

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

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

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

30% 90%

present

past
present

past future
present

past future
present

past future
present

past future
prediction hit present

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

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

Detection Strategies
are metric-based queries
to detect design flaws

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

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

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

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 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

System System
History Version
Class Class
History Version

System System
History Version
Inheritance
Version
Class Class
History Version

System System
History Version
Inheritance Inheritance
History Version
Class Class
History Version

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 ...

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

Hierarchy Evolution reveals evolution patterns
05
Girba etal, 20

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

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

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

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

1 2 3 4 5 6
A
B
C
D
E

{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}

{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

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

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

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