A Rationale-based Model for Architecture Design Reasoning

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12.2. Contributions is no common understanding on how to measure risks, and the risk assessment process in architecture design is not well understood. It suggests that further investigation in this area is required. It has been found that the methodology and tool support for design rationale capture and retrieval is inadequate. The various tools that have been reported, including word processors and UML-based tools, do not have traceability features to support systematic design rationale description and retrieval. Therefore, it is important to understand how best to capture, represent and use design rationale and then develop tools to provide a design rationale enabled development environment. In summary, the survey has allowed us to gain an in-depth understanding of the application of design rationale in the software industry. It has confirmed that even architects consider them to be useful, there is little in terms of methodology and tools to support their applications. The survey has established the need to further study architecture design rationale, and clarified a number of important research questions that we address in this thesis. 12.2.2 Design rationale representation In this thesis, we have introduced a rationale-based architecture model (AREL) to represent architecture design rationale. The AREL model uses two types of reasoning support: motivational reasons and design rationale. Motivational reasons induce architecture issues that need to be resolved. Architecture design decisions are justified by architecture design rationale which is comprised of qualitative rationale, quantitative rationale and alternative design options. In an architecture design, intricately inter-dependent design objects often have common requirements, assumptions, constraints and decisions. They can be explicitly related and reasoned in AREL models. This reasoning support complements the documentation of design structures and interfaces commonly appeared in design specifications. AREL captures two types of design rationale: qualitative design rationale QLR and quantitative design rationale QNR. QLR represents the reasoning and the arguments, in a textual form, for and against a design decision. QNR uses indices to indicate the relative costs, benefits and risks of design options. Together they can help architects justify architecture decisions. This representation is an improvement over the argumentationbased methods because it simplifies the representation of qualitative argumentation, and provides quantification to justify why a design is chosen over its alternatives. The AREL model is extended by eAREL to support design evolution. Both AREL and eAREL 207
12.2. Contributions implementations use UML for easy adoption by the software industry. The AREL model representation is an improvement over existing types of design rationale methods described in Chapter 3 because it: (a) provides a structured approach to capturing architecture rationale; (b) provides comprehensive reasoning that encompasses both qualitative and quantitative design rationale; (c) associates architecture rationale to architecture elements in reasoning. We have demonstrated the application of the AREL model in a real-world system using an electronic payment system. In an empirical study, expert architects in the area of electronic payment system have been asked to compare traditional design specifications and the AREL model. They have found that the AREL model complements the design specifications to provide a better explanation of the design reasoning of the system. 12.2.3 Design rationale applications Architecture design completeness One of the issues in software architecture is the the difficulty of articulating what is a complete architecture design. This issue directly affects how much design details architects have to carry out to be certain that the architecture is viable and complete. Using AREL as a basis, we have introduced Architecture Rationalisation Method (ARM) to facilitate the architecture design process. ARM uses the risk indices in QNR to guide architecture decomposition. By considering the implementation risks (ICR) and outcome certainty risks (OCR), architects can determine that an architecture is complete when these risks are at an acceptable level and all major requirements have been addressed. This process of using risk levels to guide architecture decisions has the benefit of assessing whether the requirements can be fulfilled and the architecture design can be implemented. It allows the architects to focus on these two aspects of architecture design until such time that they are achievable. Using the Cost-benefit Ratio (CBR) that is defined in QNR, architects can compare the relative benefits of design alternatives quantitatively. Together with QLR, they can help architects make and justify their decisions during architecture design, and these decisions can be verified independently by assessing the architecture rationale. 208
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A Rationale-based Model for Archite
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maintenance. These techniques can h
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Declaration This thesis contains no
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2.2.6 DoD Architecture Framework .
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5.4.6 Risk assessment in architectu
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8.2 The architecture rationalisatio
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12.2 Contributions . . . . . . . .
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6.10 ≪AR≫ and ≪AAR≫ Stereot
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11.13A Process to Synchronise Chang
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5.13 Design Rationale Helps Evaluat
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that architecture design is highly
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1.2. Research motivations and resea
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1.2. Research motivations and resea
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1.4. Structure of the thesis the ch
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Part I Problem Analysis 10
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2.1. Industry practice of design ra
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2.2. Architecture frameworks and de
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Chapter 3 Related work in design ra
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3.2. Why do we need design rational
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3.2. Why do we need design rational
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3.3. Existing methods for capturing
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3.4. Other related studies 3.3.7 Qu
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3.4. Other related studies evolutio
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3.5. How well design rationale meth
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3.5. How well design rationale meth
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Chapter 4 Research methodology and
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4.1. Software engineering research
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4.2. The chosen research and valida
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Part II Architecture Design Rationa
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on a regular basis. Their inputs ha
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5.1. Architecture rationale in the
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5.2. Survey methodology data collec
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5.3. Survey findings experience). I
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5.3. Survey findings Table 5.1: Fre
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5.3. Survey findings Business Goals
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5.3. Survey findings 5.3.5 Document
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5.3. Survey findings Table 5.8 summ
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5.3. Survey findings We used Spearm
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5.3. Survey findings previous desig
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5.4. Discussion of findings Since t
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5.4. Discussion of findings or cons
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5.5. Limitations and use design rat
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Part III The Representation and App
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6.1. A conceptual model for design
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6.2. Architecture Rationale and Ele
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6.2. Architecture Rationale and Ele
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6.3. Architecture elements Figure 6
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6.4. Architecture rationale Figure
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6.4. Architecture rationale • ris
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6.4. Architecture rationale depicts
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6.5. The extended AREL To prevent c
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6.6. A UML representation of AREL a
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6.6. A UML representation of AREL a
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6.7. AREL usability AE by ≪AEsupe
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6.8. Summary The AREL model is exte
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7.1. The EFT system reasoning, a co
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7.1. The EFT system The processing
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7.1. The EFT system not chosen beca
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7.1. The EFT system Figure 7.5: Int
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7.1. The EFT system sequence checki
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7.1. The EFT system Figure 7.7: Dec
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7.1. The EFT system Therefore, in a
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7.1. The EFT system Figure 7.10: De
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7.2. An empirical study to validate
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7.3. Summary The case study is spec
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8.1. Background Based on these assu
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8.2. The architecture rationalisati
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8.3. Other applications of ARM As d
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8.3. Other applications of ARM Figu
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8.3. Other applications of ARM area
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Chapter 9 Architecture rationale an
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9.1. Background 9.1 Background In t
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9.2. Traceability of architecture r
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Page 211 and 212: 11.1. Capturing architecture design
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Page 215 and 216: 11.2. Checking AREL models Figure 1
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Page 233 and 234: BIBLIOGRAPHY [10] B. W. Boehm, Soft
Page 235 and 236: BIBLIOGRAPHY [37] A. Eden and R. Ka
Page 237 and 238: BIBLIOGRAPHY [62] J. D. Herbsleb an
Page 239 and 240: BIBLIOGRAPHY [89] N. Lassing, D. Ri
Page 241 and 242: BIBLIOGRAPHY [115] D. L. Parnas,
Page 243 and 244: BIBLIOGRAPHY [142] Z. Simsek and J.
Page 245 and 246: BIBLIOGRAPHY [167] W. F. Tichy, N.
Page 247 and 248: Appendix A AREL Tool User Manual 1
Page 249 and 250: 4.1 AREL Check Model When the Check
Page 251 and 252: 4.2 AREL Model Tracing AREL model t
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Page 265 and 266: Complaint Procedure If you have any
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Page 275: IEEE Computer Society Press. A. Tan
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