Rui Pereira, Jácome Cunha, João Paulo Fernandes,Pedro Martins and João Saraiva

Refactoring meets Model-Driven Spreadsheet Evolution

QUATIC 2014Guimarães, Portugal

Spreadsheets

1

› Programming language and environment of choice for many people/companies

› 50% of all spreadsheets are the basis of decisions› 85% of companies use them for financial reporting› 11 million end-users in the USA

Spreadsheets

2

› Very error prone › Research papers on spreadsheet problems› Websites on spreadsheet problems› Google: “spreadsheet errors”

Spreadsheet Errors

3

› Only recently has this been researched (~10 years!!)› Various techniques were developed› One of them is ClassSheets

ClassSheets

4

Spreadsheets Models

ClassSheets

Instance

Instance

Instance Instance

Instance

ClassSheets: Example

5

conforms to

ClassSheets

6

› Everything is according to the model› Control of every spreadsheet› You only have to do it right once› What if you don’t do it right once?

ClassSheets Quality

7

› ClassSheets still suffer from traditional problems› Readability› Maintainability› Extensibility

› A ClassSheet may be hard to understand› May have complicated design› New rules can force changes to spreadsheet structure › Refactorings!

MDSheet

8

ClassSheet

Spreadsheet

ClassSheet’

Spreadsheet’

MDSheet

9

data ModelOperation : Model Model =-- add a new column

addColumnM Where Index-- delete a column

| delColumnM Index-- add a new row

| addRowM Where Index-- delete a row

| delRowM Index-- set a label

| setLabelM (Index, Index) Label-- set a formula

| setFormulaM (Index, Index) Formula-- replicate a class

| replicateM ClassName Direction Int Int-- add a static class

| addClassM ClassName (Index, Index)-- add an expandable class

| addClassExpM ClassName Direction (Index, Index) (Index, Index)

MDSheet

10

data ModelRefactoring: Spreadsheet [ModelOperation] =-- add a formula and shift cells

AddShiftForm ClassName Value Index Label Index-- add an attribute and shift cells

| AddShiftAtt ClassName Value Index Label Index-- delete a cell and shift cells

| DeleteShift ClassName Value Label-- add a reference and shift cells

| AddShiftRef ClassName ClassName Index-- delete a reference and shift cells

| DeleteShiftRef ClassName ClassName-- create a new class

| CreateClass ClassName Direction Index-- delete a class and shift cells

| DeleteClassShift ClassName

Refactorings

11

1. Move Formula

2. Move Attribute

3. Extract Class

4. Inline Class

5. Remove Middle-Man

Refactorings: Example

12

Refactorings: Move Formula

13

› When/Why› Feature Envy› Semantically makes more sense elsewhere

…

› Refactoring

…

Refactorings: Move Attribute

14

› When/Why› Visually enhance readability› Information evolution› Incorrect normalization in a relational class

…

…› Refactoring

Refactorings: Extract Class

15

› When/Why› Complicated and hard to understand models› Neglected subset of information

› Refactoring

Refactorings: Inline Class

16

› When/Why› Insufficient justification of the existence of a class› Not pulling its own weight› Often consulted information

› Refactoring

Refactorings: Remove Middle-Man

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› When/Why› Delegator class with little responsibility or purpose› Useless class which only complicated structure

› Refactoring

Refactorings: Final Model

18

refactorings

Refactorings: Final Instance

19

yrefactorings

Quality of Refactored Models: Quick Analysis

20

Model› Removed one class

› Organized data to be semantically correct

› Readability

› Joining attributes closer to their formulas

› Placed often used attributes in easier to access areas

Instance› 14 less data cells (15% reduction)

› One more Client 22 less cells (17% reduction)

› Two more Clients 30 less cells (18% reduction)

› Larger our instances, more impactful are the refactorings

› Spreadsheet bad smell detector also showed a reduction in smells

Conclusions and Future Work

21

› Presented a set of refactorings for ClassSheets› Implemented in a tool› First analysis shows model quality improvement› Further validation

› Quality assessment metrics› Empirical studies with professionals who use models daily

› More info?› http://ssaapp.di.uminho.pt› Read the paper› Ask me!

Rui Pereira, Jácome Cunha, João Paulo Fernandes,Pedro Martins and João Saraiva

Refactoring meets Model-Driven Spreadsheet Evolution

QUATIC 2014Guimarães, Portugal