Overview

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Software EngineeringProf. 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 EntwicklertagMay 9th, 2012

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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

Analysis

DesignCode

Test

Reuse

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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”

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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

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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

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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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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

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Test-Driven Search

■ most practical way of evaluating a component’s “fitness for purpose” is to test it -■ can deliver 100% precision

identify desiredinterface

compilecomponents

find matching components

establish acceptability

through tests

reuse

public void testTitleRetrieval () {

Movie movie = new Movie("Star Wars", 0);assertTrue(movie.getTitle ()

. equals("Star Wars"));}

public void testTitleRetrieval () {

Movie movie = new Movie("Star Wars", 0);assertTrue(movie.getTitle ()

. equals("Star Wars"));}

b)

c)

d)

e)

define desired semantics as tests

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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); ….}

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Test Driven Search (Merobase)

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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

■ …

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Test Driven (Code Conjurer)

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Proactive Recommendation Example

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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: [email protected]

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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

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