Modularization of Legacy Features by Relocation and Reconceptualization: How Much is Enough?

Modularization of Legacy Features by Relocation and Reconceptualization:

How Much is Enough?

— ―

Andrzej Olszak and Bo Nørregaard Jørgensen

Agenda

I. Prologue: The Case of NDVisII. Relocation & ReconceptualizationIII. Experimental DesignIV. Results

— 2 —

— 3 —

Prologue

“Can you help us to migrate NDVis to the NetBeans Module System?”

— 4 —

Dividing the monolith

Module System ≠ modularity Features are great candidates for

Modules!Feature is the unit of program functionality

…but getting there is difficult

— 4 —





Cont ro l l e r

Mode l

View

feature A feature B feature C

— 4 —





Cont ro l l e r

Mode l

View


Scattering

— 4 —





Cont ro l l e r

Mode l

View


Scattering

Tangling

— 5 —

The case of NDVis

Mixin layers, aspects, etc. “Let’s stick to Java”

Independent feature-modules Reusable core modules

+ →

NDVis monolith

Featureous tool

— 6 —

“Can we learn more about these restructurings?”

— 7 —

Treatment of classes! Relocation

i.e. move-class refactoring Simple Automatable Classes remain tangled

pkg2

pkg1


— 7 —



pkg2

pkg1


→feature A feature Bfeature C

— 7 —



pkg2

pkg1


→→

feature A feature Bfeature C

— 7 —



Reconceptualizationi.e. move-method refactoring Complex Inherently manual Untangles classes

pkg2

pkg1


→→


feature B

feature A

Student

feature C

— 7 —



Reconceptualizationi.e. move-method refactoring Complex Inherently manual Untangles classes

pkg2

pkg1


→→


feature B

feature A

Student

feature C

→Studentread()eat()sleep()

feature B

feature C

feature A

— 8 —

Experimental construct

Tang

ling

in p

kgs

Scattering in pkgs

Original design

— 8 —


Tang

ling

in p

kgs

Scattering in pkgs

Original design

Manual relocation + reconceptualization

— 8 —


― Q1 ―Manual modularization vs. Max relocation?

Tang

ling

in p

kgs

Scattering in pkgs

Max relocation

Original design


— 8 —



― Q2 ―Isolated impact of manual reconceptualization?

Tang

ling

in p

kgs

Scattering in pkgs

Max relocation

Original design


Max relocation + manual reconceptualization

— 8 —



― Q2 ―Isolated impact of manual reconceptualization?

― Q3 ―Relative impact of manual reconceptualization?

Tang

ling

in p

kgs

Scattering in pkgs

Max relocation

Max reconceptualization

Original design


Max relocation + manual reconceptualization

— 9 —

Q1: Automatic Relocation design

Maximum relocation No reconceptualization

Multi-objective relocation of classes in original program—Scattering—Tangling—Cohesion—Coupling

Automatic relocation significantly more efficient Time-intensity: 35 hours vs. 5 minutes

0.05 0.1 0.15 0.2 0.25 0.3

0

0.05

0.1

0.15

0.2

0.25

Scattering

Tan

glin

g

Original

Manual

Automatic

— 10 —

Q2: Manual+Automatic design

Maximum relocation Manual reconceptualization

Multi-objective relocation of classes in manual design

Contribution of manual reconceptualization is minor

Manual approach better at selected features

0.05 0.1 0.15 0.2 0.25 0.3

0

0.05

0.1

0.15

0.2

0.25

Scattering

Tan

glin

g

Original

Manual

Manual+Automatic

Automatic

— 11 —

Q3: Automatic Split design Maximum relocation Maximum reconceptualization

Simulated clean splits in manual design

Multi-objective relocation of classes in resulting design

Manual restructuring achieved a high degree of reconceptualization

Maximum effects of reconceptualization << relocation

0.05 0.1 0.15 0.2 0.25 0.3

0

0.05

0.1

0.15

0.2

0.25

Scattering

Tan

glin

g

Original

Manual

Manual+Automatic

Automatic

split

AutomaticStuden

tread()eat()sleep()feature

B

feature C

feature A

— 12 —

Conclusions

Reconceptualization with mixin layers or aspects would not give us a lot…

Focus on relocation – reconceptualize sparingly Dynamic dependencies among features Module system constraints

Better yet: Relocate automatically before you

reconceptualize!

― END ―

Controller

Model

View

feature Afeature B

feature C

Treatment of classes

→→

feature Afeature B

feature C

→

Studentread()eat()sleep()

feature B

feature C

feature Bfeature C

Student

feature C

feature B

eat(){ if (values.length==0){ read(); return; }

this.numbers = values; number = values.length; quicksort(0, number - 1);

}

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Modularization of Legacy Features by Relocation and Reconceptualization: How Much is Enough?

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