1. Towards Maintenance Support for Idiom-based Code Using Sequential Pattern Mining Tatsuya Miyake Takashi Ishio Katsuro Inoue

2. copy- and- paste while (iter.hasNext()) { Item item = (Item)iter.next(); buf.append(item.toString()); } while (iter.hasNext()) { Item item = (Item)iter.next(); buf.append(item.toString()); } code2 code1 reuse the idiom while (iter.hasNext()) { Datadata = (Data)iter.next(); buf.append(process(data)); buf.append(data.toString()); } code3 Code derived from an idiom • An idiom is a code fragment to implement a particular kind of concern. AOASIA3

3. copy- and- paste while (iter.hasNext()) { Item item = (Item)iter.next(); buf.append(item.toString()); } while (iter.hasNext()) { Item item = (Item)iter.next(); buf.append(item.toString()); } code2 code1 reuse the idiom while (iter.hasNext()) { Datadata = (Data)iter.next(); buf.append(process(data)); buf.append(data.toString()); } code3 A defect crosscutting modules • A company reuses many idioms in a software. • An idiom often spread across several systems. • When a defect is found in an idiom, developers have to inspect all instances of the idiom. • A similar problem is well-known in code-clone research, but code clone does not cover idioms. AOASIA3

4. Our research goal • To detect all instances of an idiom, we are planning to combine three approaches: Pattern Mining: sequential patterns Idiom-based Code Aspect Mining: crosscutting concern code Code Clone Detection: copy-and-pasted code AOASIA3

5. A B C ×3 E B C ×2 D F C ×2 Sequential Pattern Mining sequence database • Sequential pattern mining extracts frequent subsequences from a sequence database. • We apply prefixspan to a sequence database extracted from Java software. A B C D E A E B C A E D F B C A D B F C Sequential pattern AOASIA3

6. Sample.hoge() A.foo() IF A.bar() END-IF Sequence Database Extraction from Java Software • Sequence element of java source code • Method call element • IF/ELSE/END-IF element • LOOP/END-LOOP element • A sequence is extracted from a java method void sample () { hoge (); i =a.foo(); if( i == 0 ) { k = i; a.bar(); } } Sequence Element of Sequence AOASIA3

7. Preliminary Case Study • We applied sequential pattern mining to Java source code to detect idiom-based code. • The target software is JHotDraw • We inspected whether the instances of a pattern contribute to a single concern or not. AOASIA3

8. Application Specific Patterns org.jhotdraw.standard. DuplicateCommand public void execute() { super.execute(); setUndoActivity(createUndoActivity()); FigureSelection selection = view().getFigureSele・・・ // create duplicate figure(s) FigureEnumeration figures = (FigureEnumeration) ・・ getUndoActivity().setAffectedFigures(figures); view().clearSelection(); 　　・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ } • Example of an idiom for undo • Extracted from many classes, the pattern might be related to a crosscutting concern setUndoActivity() createUndoActivity() getUndoActivityI() setAffectedFigures() org.jhotdraw. standard.ResizeHandle public void invokeStart(int x, int y, DrawingView view) { setUndoActivity(createUndoActivity(view)); getUndoActivity().setAffectedFigures(new Sing ・・ ((ResizeHandle.UndoActivity)getUndoActivity()).se・・ } AOASIA3

9. Patterns of Implementation Idioms org.jhotdraw.standard.StandardDrawingView public void addAll(Collection figures) { FigureEnumeration fe = new FigureEnumerato・・・ while (fe.hasNextFigure()) { add(fe.nextFigure()); } } • Not application specific pattern • In aspect mining, this kind of pattern is not interested. • Maybe useful for developers inspecting idiom Sequential Pattern ( Iteration ) FigureEnumeration.hasNextFigure() while FigureEnumeration.nextFigure() } org.jhotdraw.standard.CompositeFigure public FigureEnumeration figures(Rectangle ・・・ if (_theQuadTree != null) { 　　　・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ while (fe.hasNextFigure()) { Figure f = fe.nextFigure(); //int z = fFigures.indexOf(f); l2.add(new OrderedFigureElement(f, ・・ } ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ } AOASIA3

10. The Difference from Code Clone Detection Tool The patterns extracted by Sequential pattern mining tool org.jhotdraw.standard.CutCommand public void execute() { super.execute(); setUndoActivity(createUndoActivity()); FigureEnumeration fe = view().selection(); List affected = CollectionsFactory.current().createL・・・ Figure f; FigureEnumeration dfe; while (fe.hasNextFigure()) { f = fe.nextFigure(); affected.add(0, f); dfe = f.getDependendFigures(); 　　　　・・・・・・・・・・・・・・・・・・・・・ } fe = new FigureEnumerator(affected); getUndoActivity().setAffectedFigures(fe); UndoActivity ua = (UndoActivity) getUndoActivity(); ua.setSelectedFigures(view().selection()); copyFigures(ua.getSelectedFigures(), ua.getSele・・・・ deleteFigures(getUndoActivity().getAffectedFigures()); view().checkDamage(); } The code extracted by code clone detection tool org.jhotdraw.fiures.GroupCommand public void execute() { super.execute(); setUndoActivity(createUndoActivity()); getUndoActivity().setAffectedFigures(view().selection()); ((GroupCommand.UndoActivity)getUndoActivity()).group・・・ view().checkDamage(); } org.jhotdraw.standard.AlignCommand public void execute() { super.execute(); setUndoActivity(createUndoActivity()); getUndoActivity().setAffectedFigures(view().selection()); ((AlignCommand.UndoActivity)getUndoActivity()).alignA・・・ view().checkDamage(); } AOASIA3

11. Summary • Sequential pattern mining found idiom-based code • Crosscutting concern • Implementation Idiom • Not application-specific patterns • Useful information for software maintenance • Combining with code clone detection is valuable • The result of sequential pattern mining is different from the result of code clone detection • We need further case studies on other software systems AOASIA3

12. Future Direction • Combining this approach and code clone analysis • detecting all code fragments derived from an original idiom • Support for inspecting idiom-based code crosscutting modules. • Aspect mining based on sequential pattern mining • Sequential pattern mining capture an idiom that is crosscutting modules and interleaving with other code fragments • Distinguishing a crosscutting concern from implementation idioms AOASIA3

13. AOASIA3