The scope of this research lies within the context of software engineering to improve SA and its evaluation techniques. While the current deficiencies in SA descriptions and SAE mech- anisms are discussed, the development and evaluation of a completely new SAE framework within a more general context is beyond the scope of this thesis.
Using the operational view of the Department of Defence Architecture Framework (DoDAF), the structure of this thesis is depicted in a System Modelling Language (SysML) activity dia- gram; Object Management Group (OMG),Weilkiens[2007, p257–264], as shown in Figure 1.1. The vertical swim-lanes (partitions) of the activity diagram in Figure 1.1, show how this thesis has been organised into three parts, each part comprising two or more chapters. The rounded boxes are the research activities that represent the chapters of this thesis, and the directional ar- rows between the boxes represent the flow of ideas, inputs, and outputs. The commented green boxes represent key contributions made by the research and the output of each activity.
The dependency relationships between chapters and appendices are illustrated in the pack- age diagram in Figure 1.2.
Through reading the Preface, the reader can gain a concise overview; however, further summary details can be gained by reading the introduction to each chapter of (PART II).
1.4. THESIS SCOPE AND STRUCTURE
Typographical and other conventions
Within the structure of this Thesis, there are several emphasising styles being used as follows:
• Each key concept is described in a separate section.
• Within the text of this Thesis, the names of key concepts, important words, phrases, or sentences are printed in italic font and/or bold font.
• Some of the most important paragraphs include comments, findings, summaries of sections, and key concepts are placed on a grey box such as this.
• Figure and table numbers that start a with ‘letter’ are a reference to their placement in an Appendix of the same letter.
1.4. THESIS SCOPE AND STRUCTURE
Figure 1.2: Dependency relationships between chapters and appendices: Package Diagram.
1.4.1
Introduction (PART I)
The first part (PART I) of the thesis comprises two chapters and two associated appendices (A and B):
In Chapter 1, I outline the motivation, aims, scope, and structure of the research.
A literature review is reported and discussed in Chapter 2. The findings of the analysis are reported in three main areas: i) SA descriptions and formality level, ii) model driven methods of SA in architectural context, and iii) SAE. Also, this preliminary research explores the potential “forces” that have an effect on softwarestyle/patterndescriptions, modelling techniques, and standardisation. A comparison between existing software architecture evaluation methods and categorizations of quality characteristics has been investigated, analysed and reported. This background study of the current state-of-the-art highlighted challenges and gaps within SA and SAE.
1.4.2
Contribution (PART II)
The second part (PART II) of this thesis comprises four chapters, Chapter 3 to Chapter 6. In Chapter 3, and associated Appendix C, I present an in-deep investigation and analysis of
six reliable software pattern resources in the context of their relations to quality characteristics. The study findings are stored in a database. Issues raised from the analysis are illustrated and discussed.
The results of a questionnaire-based survey are in Chapter 4 and associated Appendix D . These relate to tSPs utilisation factors. The survey was undertaken in order to support and enhance, or otherwise, an understanding of the value of Chapter 3 outcomes, and to identify any issues related to the usability of SPs amongst software engineers and developers.
Illustration of the challenging factors that have an effect on software architecture modelling and evaluation techniques are captured through a second survey questionnaire and a field study, with the results reported in Chapter 5 and associated Appendix E.
Both questionnaires in Chapter 4 and 5 were distributed to software developers within six countries. The degree of experience in software engineering of each participants varied sig- nificantly, but no participant had less than 5 years experience. Whereas, the field study was conducted in a military site during the development of many large-scale systems by several in- ternational companies, which means that these large scale Information Technology (IT) projects joined highly experienced people from both industrial and military domains.
In Chapter 6 and associated Appendix F, I provide a case study through an exploration and critique of an architecture reference model called “Real-time Control System (RCS)”. In this chapter, I demonstrate the robust relations between SA, SPs, and QAs. I also explain how they are bound together and affect each other through a well-known architecture utilised in industry. Furthermore, this chapter introduces an evaluation concept for SA, including an example to explain how the model works.
1.4.3
Wrapping up (PART III)
The third part (PART III) of the thesis is formed by one chapter, Chapter 7 titled “Discussion and Conclusion”. In Chapter 7 and associated Appendix G, I present a summary of the research work and its limitations, together with my conclusion and suggestions for further research.
In the future work section, I propose twoinitial concepts: first is System Architecture Eval- uation – SysAE profile, to evaluate both hardware and software architectures. The second con- cept is an evaluation framework and model named SAQEF, for evaluating software architecture quantitatively. Although the rationale and justification of both concepts are briefly described in Appendix G, I have included these two concepts in the future work section, as they need more research and development to fully prove their applicability in the problem domain.