Mining Logical Clones in Software:Revealing High-Level Business &

Programming RulesWenyi Qian1, Xin Peng1, Zhenchang Xing2, Stan Jarzabek3, Wenyun Zhao1

1Fudan University, China2Nanyang Technological University, Singapore3National University of Singapore, Singapore

Logical Clones

• may not well documented• revealing high-level rules

Logical Clones

• Logical clones consisting of:–Similar methods–Similar code fragments–Similar entity classes–Persistent data projects

Logical Clones

• Today’s techniques on clone/similarity detection:– Simple clone (text, token, AST…)– Structural clone (simple clone)– Similar design structures (similarity metrics, machine learning)

• They are not enough to detect high-level clones:– lack of high-level information– need of pre-defined templates, such as certain design pattern

Approach Overview

input

abstraction

output

Program Model

• Methods & functional clusters• Entity classes• Code clones• Persistent data objects

Program Model

• Methods & functional clusters– Semantic clustering

Program Model

• Entity classes– Encapsulating information with getter/setter

Program Model

• Code clones– Simple clones in different methods

Program Model

• Persistent data objects– Data tables in DB or data entries in files

Mining Process

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<Method> <Method>

<Method>

<Method>

<Method>

<Entity class>

<Entity class>

<Entity class>

Mining Process

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<Method> <Method>

<Method>

<Method>

<Method>

<Entity class>

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<Entity class>

Mining Process

Mining Process

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PosPayCheck

PosScreenprocessPay

PosPayGiftCard

PosClearPayment

PosScreen

<Method> <Method>

<Method>

<Method>

<Method>

<Entity class>

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Mining Process

Mining Process

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<Method> <Method>

<Method>

<Method>

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Mining Process

Tool: MiLico

Case Study

• Project: Opentaps 1.4.0– 14,351 classes & interfaces– 253,743 methods

• 1690 logical clones mined– at least 3 nodes & 2 instances

Case Study

Categories of Logical Clones

• Categories of Mined Logical Clones (manual work)– Programming Convention (37%)– Design Structure (24%)– Business Task (23%)– Business Process (16%)

Categories of Logical Clones

• Programming Convention– Similar ways to implement similar functions

Categories of Logical Clones

• Design Structure– Similar interaction structures

Categories of Logical Clones

• Business Task– Similar ways to implement similar business task

Categories of Logical Clones

• Business Process– Similar business process or sub-process

Human Study

• 5 senior graduate students, 2 questions:• Helpful for Programming understanding?• Helpful for Reuse/Evolution?

Human Study

Human Study

• 5 senior graduate students, 2 questions:• Helpful for Programming understanding?

YES• Helpful for Reuse/Evolution?

YES

Discussion

• Helpful for reuse, without knowledge of code details

• Developers with good domain knowledge will use logical clones better

• Making MiLiCo integrated with IDEs will make logical clones more useful

Conclusion

• The concept of logical clones• The approach for mining logical clones• The tool: MiLoCo• A case study, showing that logical clones

are helpful in software understanding, reuse and maintainance

Thanks for your attention!