1. 1 Software Engineering Prof. Dr. Colin Atkinson 1 Overview 1.Find out why software engineering is important ■ see some software engineering failures 2.Get acquainted with – ■ the Chair of Software Engineering ■ the research ■ the people ■ the teaching Accelerating Agile Development through Software Reuse Colin Atkinson Karlsruher Entwicklertag May 9th, 2012

2. 2 Software Engineering Prof. Dr. 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 and cost 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 Analysis Design Code Test Reuse

3. 3 Software Engineering Prof. Dr. Colin Atkinson 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. 4 Software Engineering Prof. Dr. Colin Atkinson 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. 5 Software Engineering Prof. Dr. Colin Atkinson 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. 6 Software Engineering Prof. Dr. Colin Atkinson 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 ■ ….

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9. 9 Software Engineering Prof. Dr. Colin Atkinson 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. 10 Software Engineering Prof. Dr. Colin Atkinson 10 Test-Driven Search ■ most practical way of evaluating a component’s “fitness for purpose” is to test it - ■ can deliver 100% precision identify desired interface compile components find matching components establish acceptability through tests reuse public voidtestTitleRetrieval() { Moviemovie= newMovie("StarWars", 0); assertTrue(movie.getTitle().equals("StarWars")); } public voidtestTitleRetrieval() { Moviemovie= newMovie("StarWars", 0); assertTrue(movie.getTitle().equals("StarWars")); } b) c) d) e) define desired semantics as tests

11. 11 Software Engineering Prof. Dr. Colin Atkinson 11 Test Driven Search Example ■ desired interface ■ excerpt of JUnit test public class Mortgage { public Mortgage(double rate, int years, double loan) {} public double MonthlyPayment() {} public double TotalPayment() {} } 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. 12 Software Engineering Prof. Dr. Colin Atkinson 12 Test Driven Search (Merobase)

13. 13 Software Engineering Prof. Dr. Colin Atkinson 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. 14 Software Engineering Prof. Dr. Colin Atkinson 14 Test Driven (Code Conjurer)

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16. 16 Software Engineering Prof. Dr. Colin Atkinson 16 Proactive Recommendation Example

17. 17 Software Engineering Prof. Dr. Colin Atkinson 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/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. 18 Software Engineering Prof. Dr. Colin Atkinson 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