Overview

1. Overview • Find out why software engineering is important • see some software engineering failures • Get acquainted with – • the Chair of Software Engineering • the research • the people • the teaching Accelerating Agile Development through Software Reuse Karlsruher Entwicklertag May 9th, 2012 Colin Atkinson

2. Reconciling Agility and Reuse • software reuse and agile development have the same underlying goal - • to allow new applications to be built more rapidly andcost effectively • but they are usually not applied at the same time • agile processes almost exclusively focus on developing new software • Challenge  • make reuse a central part of agile development Test Analysis Code Reuse Design

3. Component Reuse • Software Reuse • “the process of creating software systems from existing software rather than building software systems from scratch.” [Krueger 92] • software component markets famously proposed by McIlroy in 1968 [McIlroy 68] • the “holy grail” of software engineering, but has failed to take off to the extent expected or desired • Software Component • any cohesive and compact unit of software functionality with a well defined interface • includes simple programming language classes as well as more complex artefacts such as web services and EJBs • not focussed on “snippets”

4. Why “Reuse” Did Dot Take Off • Historically, there were there main barriers to systematic component reuse • Not enough good components to reuse • 200 was considered a lot of components in the golden years of reuse research (1980s and 1990s) • Crude retrieval technology • often returned a high proportion of unsuitable components or missed many relevant ones • Unfavourable risk/effort balance • chances of success through reuse too low to justify the effort involved

5. What’s Different Today • The situation has improved significantly since the turn of the millennium • Plenty of good components to reuse • high bandwidth internet available to all • vast repositories of open source code • web service revolution • Advanced retrieval technology • Lucene indexing engine • advanced retrieval algorithms • Radically different risk/effort balance • unobtrusive component recommendation tools becoming available

6. Merobase • One of the largest software component search engines • more than 10 million components • Public Features • multiple component types • source code, binary code, web services, Android apps • hybrid search algorithms • keyword, name, interface, .. • lookup (library, documentation, ..) • service execution • metrics • ….

9. Search Result Quality • The new generation of code search engines provides dramatically enhanced search quality • Average precision: • Signature-based search = 1% • string-based search = 16% • Name-based = 17% • Interface-based = 54% • However, this is not enough to significantly change the “build or buy” trade-off • Probability of finding component that are really “fit for purpose” is too low compared to the effort involved in exploring reuse opportunities • Need higher precision • Semantic search

10. Test-Driven Search public void public void testTitleRetrieval testTitleRetrieval () { () { Movie Movie movie movie = new = new Movie("Star Movie("Star Wars", 0); Wars", 0); assertTrue(movie.getTitle assertTrue(movie.getTitle () () . . equals("Star equals("Star Wars")); Wars")); } } • most practical way of evaluating a component’s “fitness for purpose” is to test it - • can deliver 100% precision define desired semantics as tests b) identify desiredinterface find matching components c) compilecomponents d) reuse establish acceptability through tests e)

11. Test Driven Search Example • desired interface public class Mortgage { public Mortgage(double rate, int years, double loan) {} public double MonthlyPayment() {} public double TotalPayment() {} } • excerpt of JUnit test public void testMortgage() { private Mortgage m = new Mortgage(4.5, 12, 250000); assertEquals(2250.02, m.MonthlyPayment(), 0.01); private Mortgage m = new Mortgage(4.5, 12, 250000); assertEquals(324,002.94, m.TotalPayment(), 0.01); …. }

12. Test Driven Search (Merobase)

13. Code Conjurer Eclipse Plugin • Seamlessly integrates Merobase driven search into the Eclipse development environment • Main Features • code-driven search • test-driven search JUnit test driven queries • unobtrusive (background) recommendation • component dependency resolution • interface recommendation • code metadata (metrics) • Interface adaptation • …

14. Test Driven (Code Conjurer)

16. Proactive Recommendation Example

17. Conclusion • Test-driven search fits naturally into agile, test driven development • When used together with a test-driven development strategy like XP, test-driven search makes the effort involved in finding suitable components almost zero • Is the key enabling technology for integrating reuse-oriented and agile development • can accelerate the agile development process • Get involved .. • Code Conjurer http://www.code-conjurer.org/ • use it, provide feedback, help enhance it (open source) • make your own tools search-driven • publically accessible Merobase API • create your own code search engine • merobase can crawl any content in CVS, SVN, .. repositories • Further information: atkinson@informatik.uni-mannheim.de

18. For Further reading • W. Janjic, M. Schumacher, Der Herr der Codes, Eclipse Magazin, 2.12, S&S Media GmbH, Frankfurt am Main, 2012 • O Hummel, W Janjic, C Atkinson, Code conjurer: Pulling Reusable Software out of Thin Air, IEEE Software 25 (5), 2008