Engineering Design, Complexity Metrics

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Engineering Design, Complexity Metrics

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To manage and improve engineering design processes in a methodical and systematic manner, an important issue that needs tackling is their analysis, interpretation and goal-oriented improvement. Although approaches for managing complex processes exist, a systematical, method-based analysis and improvement is still highly difficult.

To support the systematic and holistic analysis and improvement of an engineering design process, this book presents a measurement system that makes use of complexity metrics to embody various patterns of the interplay of a process’ entities (e.g. tasks, documents, organizational units, etc.). These metrics are used to draw inferences about the process’ behavior (e.g. timeliness, need for communication, forming of opinions, etc.). This way, knowledge about a process can be extracted from existing process models, or new process models can be structured systematically by addressing desirable patterns. This supports management in reducing the risks in process planning through better understanding how the structure of a process impacts the behavior of a process. Generating such a means of process analysis and management provides a major contribution both for academia and industry, especially for the improvement of large and complex engineering design processes. The metrics embody the foundations of network theory and the management of structural complexity to generate a practice-oriented application.

The metrics are supported by a meta-model for process modeling. The meta-model uses multiple-domain matrices, integrating existing process models across common domains and relationship types. The modeling method is enhanced with additional constructs of modeling that act as a bridging between existing dependency models and established process models.

Furthermore, the analysis approach is operationalized by a framework to select the metrics in accordance with the goals of the process analysis. To this end, the metrics are classified and allocated to the common goals of process analysis with regard to the structure of a process, producing eight different guidelines. To enable a flexible application, a modular set-up consisting of three steps is chosen: As a starting point, the strategic level is addressed using common goals of process analysis. Then, these goals are concretized by typical questions that can be posed in their context. Finally, these questions are answered using the metrics and parts of the meta-model.

The overall approach is detailed using three case studies from automotive development; on the one hand, the modeling and goal-oriented analysis of the body-in-white design of a premium class mid-size sedan is shown and, on the other hand, the detailed analysis and extraction of possible weak spots within the concept design, programming, and testing of electronic control units for an SUV is regarded. A third case study on general automotive design is used to illustrate all individual metrics. Results from the case studies point e.g. to particularly robust parts of the process, to criticcal structural bottle-necks, to the core drivrs for iterations or reqork, and, more generally, to potential weak spots in the overall structure of a process.

The book is based on a rigorous scientific approach to illustrate the origin of the presented results as well as the limits of their applicability. At the same time, much attention was put to illustrating all details in their industrial relevance to bridge the scientific approach and its industrial application.

Therefore, the book provides both academia and industry with new insights, above all a comprehensive collection of complexity metrics and their interpretation towards common problems in process management. It expands literature in structural complexity management into this field without limitation to its significance to other areas of application, as e.g. the design and management of complex product architectures.

At the same time, the research in this book was motivated to come “full circle”, i.e. it was created in a way that both the modeling scheme, the analysis approach and the overall guidance about how both modeling and analysis work together were integrated in a more general framework. This endeavor thus guides the overall outline of the book. Nevertheless, none of these constituents to the solution are designed to be exclusive, so that, for example, the complexity metrics can also be based on models other than the multiple-domain matrices that are used here.

TOC

1. Complex processes in engineering design 9
1.1 Preface .......................................................................................................9
1.2 A practical application: A design process at Audi AG ............................ 13
1.2.1 Description of the process ............................................................... 13
1.2.2 Modeling the process as an EPC process chart ............................... 17
1.2.3 Deficits when analyzing the process chart using existing methods . 17
1.2.4 Conclusion: Systematic analysis of a process chart ........................ 20
1.3 The need for systematic analysis in practice ........................................... 21
1.3.1 The problem: Systematic analysis of a process chart ...................... 21
1.3.2 Basic hypotheses and research questions ........................................ 23
1.3.3 The approach used in this research .................................................. 26
1.4 Context of developing complexity metrics.............................................. 26
1.4.1 Goals of this research ...................................................................... 26
1.4.2 Basic requirements of the solution .................................................. 27
1.4.3 Targeted audience ............................................................................
1.4.4 What this book is not about ............................................................. 29
1.4.5 Related fields of science .................................................................. 30
1.5 Structure of this book .............................................................................. 30
2. The foundations of complexity metrics 33
2.1 Structural complexity of a system ........................................................... 33
2.1.1 General notions of managing structural complexity ........................ 35
2.1.2 Graph Theory .................................................................................. 43
2.1.3 Matrix-based methodologies to manage structures .......................... 45
2.1.4 Network Theory .............................................................................. 52
2.1.5 Other approaches to managing complex systems ............................ 56
2.1.6 Summary ......................................................................................... 57
2.2 Structural aspects of process management .............................................. 59
2.2.1 Processes in Engineering Design ..................................................... 59
2.2.2 Goals of analyzing, improving and managing processes ................. 64
2.2.3 Process models and their structural content .................................... 66
2.2.4 Strategies to analyze design processes and models ......................... 72
2.2.5 Summary ......................................................................................... 74
2.3 Metrics to analyze the structure of a process........................................... 75
2.3.1 Basics and measurement foundation ............................................... 75
2.3.2 Metrics to describe networks ........................................................... 79
2.3.3 Metrics in software engineering ...................................................... 79
2.3.4 Metrics in process management ...................................................... 82
2.3.5 Metrics for engineering design processes ........................................ 85
2.3.6 The limits of using metrics in an organization ................................ 87
2.3.7 Summary ......................................................................................... 89
2.4 Directions from the state of the art .......................................................... 91

3. Concept of an integrated set of complexity metrics ....... 93
3.1 Solution design process ........................................................................... 93
3.2 Requirements for the solution design ...................................................... 94
3.3 Constituents of the solution ..................................................................... 95
3.4 Overall concept: Analysis procedure ...................................................... 97
4. Modeling the structure of design processes 101
4.1 Design processes as a multi-layered network ........... 101
4.2 MDM-based modeling of the structure of a process ............................. 102
4.3 The Structural Process Architecture model ........................................... 104
4.4 Specific aspects of modeling engineering design processes.................. 109
4.4.1 Alignment of the process structure with the product architecture . 109
4.4.2 Inclusion of attributes to nodes and edges ..................................... 111
4.4.3 Decision points modeled as Boolean operators ............................. 114
4.5 Building the process model ................................................................... 120
4.5.1 Generating a process model .......................................................... 121
4.5.2 Aggregate views recombining domains and relationship types ..... 123
4.5.3 Example of a process model for engineering release management .................................................................................. 130
4.6 Conclusion: MDM-based process modeling ......................................... 132

5. Complexity Metrics for Design Processes 133
5.1 Assessing structural characteristics using metrics ................................. 135
5.1.1 Basic and combined structural characteristics ............................... 135
5.1.2 Solution principles for structural metrics ...................................... 137
5.1.3 Evaluation of structural characteristics using structural metrics ... 138
5.1.4 Structural outliers .......................................................................... 142
5.2 Overview of the Structural Measurement System ................................. 143
5.2.1 A comprehensive set of complexity metrics .................................. 143
5.2.2 Relevance and limits of basic structural metrics ........................... 147
5.2.3 Relevance and limits of combined and specific structural metrics 150
5.2.4 Classification of available metrics ................................................. 157
5.3 An example application of the Structural Measurement System ........... 159
5.3.1 The process in focus ...................................................................... 159
5.3.2 Overview of the analyses using structural complexity metrics ..... 161
5.3.3 Analyses using complexity metrics for the overall process model 162
5.3.4 Analyses using complexity metrics for each task .......................... 163
5.3.5 Analyses using complexity metrics for each module .................... 167
5.3.6 Conclusions for the regarded process ............................................ 169
5.4 Conclusion: Structural metrics .............................................................. 171

6. The S-GQM framework to select metrics 173
6.1 Existing frameworks to facilitate the analysis of a system .................... 173
6.1.1 Quality Function Deployment and the House of Quality .............. 174
6.1.2 Goal-Question-Metric ................................................................... 175
6.1.3 Balanced Scorecard ....................................................................... 176
6.1.4 Directions and requirements .......................................................... 178
6.2 Systematic access to the structure of a process ..................................... 179
6.2.1 Goals and questions of structural process analysis ........................ 180
6.2.2 Allocation of metrics, domains and relationship-types ................. 185
6.2.3 Identifying structural outliers ........................................................ 187
6.2.4 Structural significance of the outliers ............................................ 187
6.3 Using and adapting the framework ....................................................... 189
6.4 Conclusion: S-GQM framework for structural analysis ........................ 190

7. Industrial application of metrics 191
7.1 Electronic control unit design: General analysis in Automotive Development .......................................................................................... 191
7.1.1 Goals and focus of the project ....................................................... 192
7.1.2 The process model used ................................................................ 192
7.1.3 Analysis and findings .................................................................... 195
7.1.4 Implications and validation ........................................................... 208
7.1.5 Reflection ...................................................................................... 210
7.2 Automotive design process at Audi AG: Analysis of interfaces ........... 211
7.2.1 Goals and focus of the project ....................................................... 212
7.2.2 The process model used ................................................................ 213
7.2.3 Analysis and findings .................................................................... 218
7.2.4 Implications and validation ........................................................... 223
7.2.5 Reflection ...................................................................................... 224
7.3 Conclusions from the case studies......................................................... 225

8. Conclusions and outlook
8.1 Summary of results ............................................................................... 227
8.2 Reflection .............................................................................................. 228
8.2.1 Strengths and weaknesses ............................................................. 228
8.2.2 Implications for industry ............................................................... 231
8.2.3 Implications for Research .............................................................. 233
8.3 Outlook.................................................................................................. 233

9. References 235

10. Appendix 271
10.1 Structural content of process modeling methodologies ......................... 272
10.2 Conversion of a process with logic operators ........................................ 288
10.3 Nesting of Boolean operators ................................................................ 295
10.4 The complete Structural Process Architecture ...................................... 297
10.5 List of structural metrics ....................................................................... 298
10.6 Computability of metrics ....................................................................... 390
10.7 Classification of metrics ........................................................................ 392
10.8 GQM-Framework for metrics ............................................................... 396
10.9 Complete results of case study 7.2 ........................................................ 398

11. Keyword index 401