Empirical studies for the application of agile methods to embedded systems [Elektronische Ressource] / vorgelegt von Dirk Wilking

Dirkwilking

Sujets

• Informatik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2008
• Nombre de lectures: 25
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Aachen
Department of Computer Science
Technical Report
Empirical Studies for the Application of
Agile Methods to Embedded Systems
Dirk Wilking
ISSN 0935{3232 Aachener Informatik Berichte AIB 2008 19
RWTH Aachen Department of Computer Science December 2008The publications of the Department of Computer Science of RWTH Aachen
University are in general accessible through the World Wide Web.
http://aib.informatik.rwth-aachen.de/Empirical Studies for the
Application of Agile Methods to
Embedded Systems
Von der Fakultat fur Mathematik, Informatik und Naturwissenschaften
der RWTH Aachen University zur Erlangung des akademischen
Grades eines Doktors der Naturwissenschaften genehmigte Dissertation
vorgelegt von
Dipl.-Inform. Dirk Wilking
aus Osterholz-Scharmbeck
Berichter: Universitatsprofessor Dr.-Ing. Stefan Kowalewskiatspr Ulrik Schroeder
Tag der mundlichen Prufung: 13.11.2008
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online
verfugbar.Dirk Wilking
Lehrstuhl Informatik 11
[e-mail]
Aachener Informatik Bericht AIB-2008-19
Herausgeber: Fachgruppe Informatik
RWTH Aachen University
Ahornstr. 55
52074 Aachen
GERMANY
ISSN 0935-3232Abstract
Agile Methods are a collection of software engineering techniques with speci c
di erences to traditional software engineering processes. The main di erences
consist of rapid, cycle based development phases setting the focus of attention
on feedback of the source code being developed. The results taken from user
feedback, software reviews, or other forms of software evaluation are used as a
basis for changes which comprise for example corrections of the user interface or
the adaption of the software architecture. Based on single techniques taken from
Agile Methods, their application to embedded systems software engineering is
empirically evaluated in this thesis.
The experiments and studies which have been conducted comprise the tech-
niques of refactoring, short releases, and test driven development. The results
hint to inconclusive e ects. For example it could be shown that a constant
e ort for functional work is achieved by using the short releases technique, but
its impact on the resulting software remains di cult to assess. For refactoring
a reduced consumption of memory was found, but this e ect was created by an
overhead for applying the refactoring technique itself.
The e ect of agile techniques appears to be inferior to individual software
development ability of participants in terms of factor strength. Consequently,
the second part of the thesis aims at creating variables for the purpose of
experiment control. Variables comprise C language knowledge and viscosity
measuring a participant’s level of reluctance to change a fragment of source
code.
An additional experiment consists of the replication of the N-version pro-
gramming experiment by Knight and Leveson. The original experiment of
independence between two program failures has been extended by an additional
factor of hardware diversity. By using di erent hardware platforms, it has
been expected to create mutual independent failures which is not approved by
experimental observations.
iiiAcknowledgments
I would like to thank Prof. Dr. Stefan Kowalewski for supporting the overall
and sometimes very ambitious aim of this thesis. Prof. Dr. Ulrik Schroeder
gave kind advice concerning the human centered approach. I would like to
thank Prof. Dr. Dr. Wolfgang Thomas and Prof. Dr. Horst Lichter for
participating in the dissertation committee.
The members of the embedded software chair must be mentioned for all the
fruitfull discussions and great cooperation. Especially the rst three Ph.D.
students, namely Dr. Bastian Schlich, Dr. Falk Salewski, and Daniel Klunder
were a strong point of motivation.
Finally, I would like to thank all my diploma students. Umar Sherwani,
David Schilli, Axel Jan en, Sven Abeln, and Ahmad Afaneh amongst others
had a strong in uence on the results and direction of this thesis.
iiiivContents
I Introduction 1
1 Motivation 3
2 Thesis Synopsis 5
2.1 Research Question . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2h Methodology . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . 8
II Experiments on Agile Techniques 9
3 Overview of Agile Methods related Experiments 11
4 Planning of Embedded Software Projects 13
4.1 The Technique of Short Releases . . . . . . . . . . . . . . . . . . 13
4.2 Design of the Experiment . . . . . . . . . . . . . . . . . . . . . 14
4.2.1 Variables and Measurement . . . . . . . . . . . . . . . . 14
4.2.2 Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.4 Participants . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.5 Threats to Validity . . . . . . . . . . . . . . . . . . . . . 16
4.3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.3.1 Quality of the Survey Data . . . . . . . . . . . . . . . . 17
4.3.2 Group Di erences . . . . . . . . . . . . . . . . . . . . . . 17
4.3.3 Main Hypothesis . . . . . . . . . . . . . . . . . . . . . . 19
4.3.4 Explorative Analysis . . . . . . . . . . . . . . . . . . . . 19
4.4 Experiment Results . . . . . . . . . . . . . . . . . . . . . . . . . 24
5 Refactoring 27
vContents
5.1 The Technique of Refactoring . . . . . . . . . . . . . . . . . . . 27
5.2 Design of the Experiment . . . . . . . . . . . . . . . . . . . . . 28
5.2.1 Variables and Measurement . . . . . . . . . . . . . . . . 28
5.2.2 Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2.4 Participants . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.2.5 Threats to Validity . . . . . . . . . . . . . . . . . . . . . 31
5.3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.3.1 Main Hypothesis . . . . . . . . . . . . . . . . . . . . . . 32
5.3.2 Analysis of Additional Variables . . . . . . . . . . . . . . 35
5.3.3 Experiment Power . . . . . . . . . . . . . . . . . . . . . 37
5.4 Experiment Results . . . . . . . . . . . . . . . . . . . . . . . . . 38
6 Test Driven Development 39
6.1 Design of the Experiment . . . . . . . . . . . . . . . . . . . . . 39
6.2 Reasons for Failure . . . . . . . . . . . . . . . . . . . . . . . . . 40
7 Summary of Findings 41
7.1 Problem of the Human Factor . . . . . . . . . . . . . . . . . . . 41
7.2 Results of Experiments . . . . . . . . . . . . . . . . . . . . . . . 41
III Experiments on the Human Factor 43
8 Overview of Human Factor related Experiments 45
9 Rasch Models 47
9.1 The Dichotomous Rasch Model . . . . . . . . . . . . . . . . . . 47
9.2 The Linear Logistics Test Model . . . . . . . . . . . . . . . . . . 48
9.3 Logit as Parameter Units . . . . . . . . . . . . . . . . . . . . . . 49
9.4 Bene ts and Drawbacks of the Rasch Model . . . . . . . . . . . 50
10 C Knowledge 53
10.1 The Concept of C Knowledge . . . . . . . . . . . . . . . . . . . 53
10.2 Design of the Experiment . . . . . . . . . . . . . . . . . . . . . 54
10.2.1 Variables and Measurement . . . . . . . . . . . . . . . . 54
10.2.2 Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10.2.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2.4 Participants . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.2.5 Threats to Validity . . . . . . . . . . . . . . . . . . . . . 56
vi