This document summarizes a seminar presentation about using a seismology-inspired approach to study change propagation in software. The approach models software changes as "earthquakes" that propagate through relationships between classes. It identifies important classes, class levels based on dependencies, and impacted classes based on historical co-changes. Important classes are identified using metrics like PageRank. Change propagation is then modeled based on these class dependencies and co-changes.

1. Soccerlab and
Ptidej team
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
A Seismology-inspired Approach
Antoniol
to Study Change Propagation
Introduction
The Earthquake
Metaphor
Salima Hassaine, Ferdaous Boughanmi, Yann-Ga¨le
Approach
Empirical Study
Gu´h´neuc, Sylvie Hamel, Giuliano Antoniol
e e
Study Results
´
SOCCER Lab. and Ptidej Team – DGIGL, Ecole Polytechnique de
Conclusion
Montr´al, Qu´bec, Canada
e e
September 27, 2011
Pattern Trace Identification, Detection, and Enhancement in Java
SOftware Cost-effective Change and Evolution Research Lab

2. Soccerlab and
Ptidej team Context and Motivation
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol Software evolves continuously, requiring continuous
Introduction maintenance and development
The Earthquake
Metaphor
Software maintenance is the most costly and difficult
Approach
phase in software life cycle
Empirical Study
Study Results
Making changes without understanding their
Conclusion
effects can lead to poor effort estimation and delays
in release schedules, because of their consequences
(e.g., the introduction of bugs, etc.)
2 / 25

3. Soccerlab and
Ptidej team Change Impact Analysis
Seminar
Salima Hassaine,
Ferdaous
Boughanmi, Change impact analysis is defined by Bohner and
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Arnold [1] as “identifying the potential consequences of
Hamel, Giuliano
Antoniol
a change, or estimating what needs to be modified to
accomplish a change”.
Introduction
The Earthquake
Metaphor
Approach
Empirical Study
Study Results
Conclusion
[1] S. A. Bohner and R. S. Arnold, Software Change Impact Analysis. IEEE
Computer Society Press, 1996.
3 / 25

4. Soccerlab and
Ptidej team Existing approaches
Seminar
Salima Hassaine,
Ferdaous Structure-based Analysis
Boughanmi,
Yann-Ga¨l
e Dependency analysis of source code is performed using
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
static or dynamic program analyses
Antoniol The relationships between classes make change impact
Introduction
difficult to anticipate (e.g., hidden propagation)
The Earthquake
History-based Analysis
Metaphor Mining software repositories to identify co-changes of
Approach software artefacts within a change-set
Empirical Study It is often able to capture change couplings that cannot
Study Results be captured by static and dynamic analyses.
Conclusion They lack to capture how changes are spread over space
(e.g., class diagram) They could not help developers
prioritise their changes according to the forecast scope
of changes
Probabilistic Approaches
Building change propagation models to predict future
change couplings using probabilistic tools (e.g.,
Bayesian Networks, Time Series Analysis, etc.)
4 / 25

5. Soccerlab and
Ptidej team Motivating example
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction
Bug ID200551 reports a bug in Rhino, that was
The Earthquake
introduced by a developer when he implemented a
Metaphor change to class Kit and missed a required change to
Approach
class DefiningClassLoader.
Empirical Study
Study Results
Information passes from class Kit to class
Conclusion
DefiningClassLoader through an intermediary class
ContextFactory that remains unchanged.
5 / 25

6. Soccerlab and
Ptidej team Our goal
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Propose an approach to study the scope of change
propagation based on a seismology metaphore
Introduction
The Earthquake
Metaphor Our approach considers changes to a class as an
Approach earthquake that propagates through a long chain of
Empirical Study relationships
Study Results
Conclusion Our approach combines static dependencies
between classes and historical co-change relations
to study how far a change propagation will proceed
from a given class to the others.
6 / 25

7. Soccerlab and
Ptidej team The Earthquake Metaphor
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction
The Earthquake
Metaphor
Approach
Empirical Study
Study Results
Conclusion
Active seismic areas “Important” classes
Earthquake Software change
Epicenter “Important” changed class
Seismic wave propagation Change propagation
Damaged sites “Impacted” classes
Distance from an epicenter Class level
7 / 25

8. Soccerlab and
Ptidej team Approach
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Step 1: Identifying the most important classes
Introduction
Using PageRank-based metric, History-based metric,
The Earthquake
Metaphor and Combination of the both metrics.
Approach Step 2: Identifying class levels
Empirical Study Using static dependencies between classes
Study Results
Step 3: Identifying impacted classes
Conclusion
Using historical co-change relations extracted from
software repositories
8 / 25

9. Soccerlab and
Ptidej team Step 1: Identifying the most important classes
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction
The Earthquake
Metaphor
Approach
Empirical Study
Study Results
Conclusion
9 / 25

10. Soccerlab and
Ptidej team Step 2: Identifying class levels (1/2)
Seminar
Salima Hassaine,
Ferdaous A
ag
F
as
G
Boughanmi,
Yann-Ga¨l
e A
ag
F
as
G
in
Gu´h´neuc, Sylvie
e e B
Hamel, Giuliano in
cr cr cr
Antoniol B dm
cr cr cr
in in in
Introduction co
C D E
in in in
The Earthquake dm dm dm dm
Metaphor C D E co
Approach
(a) UML-like model (b) Eulerian model
Empirical Study
Study Results
Conclusion (c) String representation of the Eulerian model
Figure: The conversion of a class diagram into string (from [2]).
[2] O. Kaczor, Y.-G. Gu´h´neuc, and S. Hamel, Efficient identification of
e e
design patterns with bit-vector algorithm,pp. 175–184. IEEE Computer
Society Press, 2006.
10 / 25

11. Soccerlab and
Ptidej team Step 2: Identifying class levels (2/2)
Seminar
Salima Hassaine,
Ferdaous Bit-Vector Algorithm
Boughanmi,
Yann-Ga¨l
e
Input:
Gu´h´neuc, Sylvie
e e The Epicenter Class (e.g., class A)
Hamel, Giuliano
Antoniol The String Representation of the program
Output:
Introduction
Class levels (e.g., Level0 = {A}, Level1 = {B, F },
The Earthquake
Metaphor Level2 ={D, E , C }, Level3 = {G }, Level4 = {F })
Approach
Empirical Study
Study Results
Conclusion
11 / 25

12. Soccerlab and
Ptidej team Step 3: Identifying impacted classes
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
We define a time window T of observation as the
median of time between two subsequent changes to the
Introduction
epicenter class.
The Earthquake
Metaphor
Approach We extract all the commits that happened after any
Empirical Study change to the epicenter class and within the chosen
Study Results time window T.
Conclusion
We use our framework Ibdoos to implement queries for
collecting the set of classes that changed after any
change to the epicenter class and during T.
12 / 25

13. Soccerlab and
Ptidej team Empirical Study Design
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Goal: to show the applicability and usefulness of our
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
approach
Antoniol
Purpose: to gather interesting observations on the
Introduction scope of change propagation and confirming these
The Earthquake
Metaphor
observations statistically
Approach Quality focus: is the accuracy of the identified scope of
Empirical Study change propagation
Study Results
Perspective: researchers and practitioners who should
Conclusion
be aware of the scope of a change to estimate the effort
required for future maintenance tasks. The observed
phenomena can help for making decisions concerning
the process of future software projects.
Context: three open source systems: Pooka, Rhino, and
Xerces-J.
13 / 25

14. Soccerlab and
Ptidej team Research Questions (1/3)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano RQ1: Does our metaphor allow us to observe the scope of
Antoniol
change impact?
Introduction We investigate whether it is possible to apply our
The Earthquake
Metaphor
approach to observe change propagation through class
Approach levels
Empirical Study We perform a qualitative study to confirm our
Study Results observations of change propagation, using external
Conclusion
information
Thus, we can show that, indeed, like in seismology,
certain levels are more impacted by a change than
others
14 / 25

15. Soccerlab and
Ptidej team Research Questions (2/3)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
RQ2: What is the level most impacted by a change?
Introduction
We perform a quantitative study to confirm our
The Earthquake
Metaphor observations of change propagation, using statistical
Approach tests to investigate which level may be the most
Empirical Study impacted by a change, and classifying the levels having
Study Results similar impact
Conclusion
Thus, we can deduce all classes with a higher risk to be
impacted by any change to epicenter class
15 / 25

16. Soccerlab and
Ptidej team Research Questions (3/3)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction RQ3: What is the most reachable level by a change?
The Earthquake
Metaphor As in RQ2, we perform a quantitative study to confirm
Approach our observations of change propagation, using statistical
Empirical Study tests to investigate, for each level, the number of
Study Results earthquakes that propagate until a given level.
Conclusion
Thus, we can deduce the most reachable level.
16 / 25

17. Soccerlab and
Ptidej team Analysis Methods
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e RQ1: Using the R statistical system, we build the 3D
Hamel, Giuliano
Antoniol graph visualising the change propagation from the
Introduction
epicenter class to other classes.
The Earthquake
Metaphor RQ2: We compute, for each level, the number of
Approach classes that changed after any change to the considered
Empirical Study
epicenter class.
Study Results
Conclusion
RQ3: For each level, we create a subset that contains
the number of earthquakes that stop at this level.
We conduct Duncan’s multiple range test to classify the
subsets with respect to the differences between them.
17 / 25

18. Soccerlab and
Ptidej team Study Results (1/3)
Seminar
Salima Hassaine,
Ferdaous RQ1: Does our metaphor allow us to observe the scope of
Boughanmi,
Yann-Ga¨l
e
change impact?
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction
The Earthquake
Metaphor
Approach
Empirical Study
Study Results
Conclusion
(a) class XMLEventImpl (b) class TypeValidator
Figure: Change propagation
Epicenter class XMLEntityScanner: we found the bug
ID1099 that relate the changes to the epicenter class
with changes to XMLParser (level 3).
18 / 25

19. Soccerlab and
Ptidej team Study Results (2/3)
Seminar
Salima Hassaine,
Ferdaous RQ2: What is the level most impacted by a change?
Boughanmi,
Yann-Ga¨l
e Homogenous subsets for alpha = 0.1
Gu´h´neuc, Sylvie
e e Levels Range 1 Range 2 Range 3
Hamel, Giuliano
Antoniol 5 107.5410
4 147.7778
Introduction 3 150.0000
The Earthquake 2 202.0408
Metaphor 1 354.4828
Approach
Table: Rhino: Duncan’s test applied on “number of changes”
Empirical Study
Study Results
Conclusion
Homogenous subsets for alpha = 0.1
Levels Range 1 Range 2 Range 3
6 6.4015
5 10.8485
4 24.8333
3 50.2789
2 83.7273
1 895.2652
Table: Xerces-J: Duncan’s test applied on “number of changes”
19 / 25

20. Soccerlab and
Ptidej team Study Results (3/3)
Seminar
Salima Hassaine,
Ferdaous RQ3: What is the most reachable level by a change?
Boughanmi,
Yann-Ga¨l
e Homogenous subsets for alpha = 0.1
Gu´h´neuc, Sylvie
e e Max Level Range 1 Range 2 Range 3
Hamel, Giuliano
Antoniol 5 .5833
4 1.3712
Introduction 3 1.7500
The Earthquake 2 4.6136
Metaphor 1 11.7121
Approach
Table: Rhino: Duncan’s test applied on “number of earthquakes”
Empirical Study
Study Results
Conclusion
Homogenous subsets for alpha = 0.1
Max Level Range 1 Range 2 Range 3
6 10.5333
5 16.3333
4 21.6667
3 30.0033
2 43.2000
1 54.8667
Table: Xerces-J: Duncan’s test applied on “number of earthquakes”
20 / 25

21. Soccerlab and
Ptidej team Threats to Validity (1/2)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Construct validity concerns the relation between
Introduction theory and observations. In this study, they could be
The Earthquake
Metaphor
due to the chosen time windows which may affect our
Approach
observations.
Empirical Study Internal Validity of a study is the extent to which a
Study Results treatment impacts the dependent variable. The
Conclusion internal validity of our study is not threatened because
we have not manipulated the independent variable,
extent of the change propagation.
21 / 25

22. Soccerlab and
Ptidej team Threats to Validity (2/2)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi, External Validity of a study relates to the extent to
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e which we can generalise its results. The main threat
Hamel, Giuliano
Antoniol to the external validity of our study that could affect
Introduction
the generalisation of the presented results relates to the
The Earthquake
analysed programs. Future work includes replicating this
Metaphor
study on other programs to confirm our results.
Approach
Conclusion validity threats deals with the relation
Empirical Study
Study Results
between the treatment and the outcome. We paid
Conclusion
attention not to violate assumptions of the performed
statistical tests. Thus, we improved our conclusion
validity by increasing the risk of making a Type I error
(increase the chance that we will find a relationship
when in fact there is not), we can do that statistically
by raising the alpha level. For instance, instead of using
0.05 significance level, we use 0.1 as our cutoff point.
22 / 25

23. Soccerlab and
Ptidej team Conclusion (1/2)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol We proposed an approach to study how far a change
Introduction propagation will proceed from a given class to the
The Earthquake others.
Metaphor
Approach
We performed a qualitative and two quantitative
Empirical Study
studies. We showed that our intuition, about the
Study Results
impacted classes by a change must be near to the
Conclusion
changed class, is incorrect in some cases. However,
there are some change propagations that reach the 5th
level in Rhino (and 6th in Xerces-J).
23 / 25

24. Soccerlab and
Ptidej team Conclusion (2/2)
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Identifying the scope of change propagation could help,
Introduction
both developers and managers. Developers could locate
The Earthquake
Metaphor easily the change impact. Managers could estimate the
Approach efforts required to perform changes more accurately.
Empirical Study
Study Results Future work: Apply our metaphor and our approach to
Conclusion other programs to confirm our observations. We will
also adapt seismology models to predict changes to
classes.
24 / 25

25. Soccerlab and
Ptidej team Questions?
Seminar
Salima Hassaine,
Ferdaous
Boughanmi,
Yann-Ga¨l
e
Gu´h´neuc, Sylvie
e e
Hamel, Giuliano
Antoniol
Introduction
The Earthquake
Metaphor
Approach
Empirical Study
Study Results
Conclusion
25 / 25