1) The document summarizes a master's thesis defense about building an Eclipse plugin called Mendel to recommend code changes to developers based on regularities extracted from existing code. 2) Mendel uses a "genetic metaphor" to find family members of a selected code entity according to different family definitions, extract dominant traits from the family, and recommend traits for the entity that are not already implemented. 3) The thesis validates Mendel's recommendations by analyzing multiple versions of projects and checking if recommended changes were later implemented by developers. The results showed some family definitions were better suited than others for different recommendation types.

1. Building an Eclipse plugin to
recommend changes to developers
Master thesis defense – June 2013
Snaps François – Université catholique de Louvain – EPL
Advisor & Guidance – Prof. Kim Mens & Dr. Angela Lozano
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Master thesis defense

2. Context
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Maintenance and extension of existing systems
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Frequent and complex operations
Difficulty: developers need to interact with unfamiliar code
Before becoming productive, a developer needs to know:
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The limits and bounds of the existing system
Where and how to integrate his modifications in the system
The conventions, coding idioms, etc…
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Master thesis defense

3. Solution
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Build a tool to facilitate this interaction between the
developer and the existing system
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Mendel’s approach:
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Extract regularities from an existing system
Recommend implementation hints
as changes to the developer
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Master thesis defense

4. Mendel: a Genetic Metaphor
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“Tell me who your family is, I will tell you what you should
look like”
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Select an entity
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Find its family members according to a family definition
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Extract dominant and recessive traits of the family
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Family definition (in this example):
all apples belonging to the previous picture
Dominant trait: “color: green” is shared by all other family members
Recommend family trait not implemented by the selected entity
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Recommendation: the selected apple should also have the color green
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Master thesis defense

5. Family Definition: a Key Factor
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What if, instead of the previous definition, we now use
this definition:
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All apples belonging to the same tree as the selected apple
Ø No more “color: green” trait recommended
Ø Possible other family traits (taste, form,…)
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Objective: supporting multiple family definitions
Study the impact of the family definition on:
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The quality of the recommendations produced
The type of the recommendations produced
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Master thesis defense

6. Predefined families
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Default family (Mendel definition)
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For classes & interfaces : all siblings and nephews of the
selected class or interface
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+ distinction between abstract and concrete classes.
For methods : all methods with the same name as the selected
method within the siblings and nephews of the selected
method’s class.
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Master thesis defense

7. Predefined families
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Identifiers Family
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Implements Family
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Relation: part of the entity’s
name
Parameterized family
Relation: implements and
extends links
Specialized family: classes and
interfaces
Callers Family
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Relation: method called
Parameterized family
Specialized family: methods
and constructors
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Master thesis defence

8. Validation
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Hypothesis : a “relevant” recommendation is one that has
actually been implemented by developers
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Technique : analyzing multiple versions of a same project
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Produce recommendations for each version
Verify if these recommendations are implemented in a later
version
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Master thesis defense

9. Validation: implementation
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Multiple parsing issue
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Particularity of Mendel’s approach
Solution used: database
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Extractor tool
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Parses the entire source code of the version and stores it into the
database
Validation on the database
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Master thesis defense

10. Results
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Some family definitions are more suited for some
recommendations types than others
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“Method implemented” type
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Implements family
23 of 1505 recommendations are actually implemented
¨ 41 of 50 recommendations are rated as relevant
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Identifiers family (M2)
0 of 828 recommendations are actually implemented
¨ 22 of 50 recommendations are rated as relevant
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Master thesis defense

11. Future Work
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Improve the validation filters
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Better family thresholds
Better family definitions
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Restrict the number of entities analyzed
Restrict the number of irrelevant recommendations produced
Example: “extends” type and our Default family
Validation with real users
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Master thesis defense

12. Conclusion
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Supporting multiple family definitions
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Allows to select the most appropriate family for a type of
recommendation
Avoids the case where a family definition struggles to produce
some recommendation types
Allows to compare recommendations from a different point of
view (different family definitions)
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Master thesis defense