Introducing Mode Switch in Component-Based Software Development

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Mälardalen University Press Dissertations No. 188

INTRODUCING MODE SWITCH IN

COMPONENT-BASED SOFTWARE DEVELOPMENT

Hang Yin

2015

School of Innovation, Design and Engineering Mälardalen University Press Dissertations

No. 188

INTRODUCING MODE SWITCH IN

COMPONENT-BASED SOFTWARE DEVELOPMENT

Hang Yin

2015

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INTRODUCING MODE SWITCH IN COMPONENT-BASED SOFTWARE DEVELOPMENT

Hang Yin

Akademisk avhandling

som för avläggande av teknologie doktorsexamen i datavetenskap vid Akademin för innovation, design och teknik kommer att offentligen försvaras

torsdagen den 29 oktober 2015, 14.15 i Beta, Mälardalens högskola, Västerås. Fakultetsopponent: Professor Carlo Ghezzi, Politecnico di Milano, Milano, Italy

ISBN 978-91-7485-229-5 ISSN 1651-4238

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Hang Yin

Akademin för innovation, design och teknik

Hang Yin

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Abstract

Self-adaptivity, characterized by the ability to dynamically adjust behavior at runtime, is a growing trend in the evolution of modern embedded systems. While self-adaptive systems tend to be flexible and autonomous, self-adaptivity may inevitably complicate software design, test and analysis. A strategy for taming the growing software complexity of self-adaptive systems is to partition system behaviors into different operational modes specified at design time. Such a multi-mode system can change behavior by switching between modes at runtime under certain circumstances. Multi-mode systems can benefit from a complementary approach to the software development of complex systems: Component-Based Software Engineering (CBSE), which fosters reuse of independently developed software components. However, the state-of-the-art component-based development of multi-mode systems does not take full advantage of CBSE, as reuse of modes at component level is barely addressed. Modes are often treated as system properties, while mode switches are handled by a global mode manager. This centralized mode management entails global information of all components, whereas the global information may be inaccessible in component-based systems. Another potential problem is that a single mode manager does not scale well, particularly at design time, for a large number of components and modes. In this thesis we propose a distributed solution to the component-based development of multi-mode systems, aiming for a more efficient and scalable multi-mode management. Our goal is to fully incorporate modes in software component reuse, supporting reuse of multi-mode components, i.e., components able to run in multiple modes. We have developed a generic framework, the Mode-Switch Logic (MSL), which not only supports reuse of multi-mode components but also provides runtime mechanisms for handling mode switch. MSL includes three fundamental elements: (1) a mode-aware component model with the formal specification of reusable multi-mode software components; (2) a mode mapping mechanism for the seamless composition of multi-mode components; and (3) a mode-switch runtime mechanism which is executed by each component in isolation from its functional execution and coordinates the mode switches of different components without the need of global mode information. The mode-switch runtime mechanism has been verified by model checking in conjunction with mathematical proofs. We also provide a mode-switch timing analysis for the runtime mechanism to respect real-time requirements.

MSL is dedicated to the mode aspect of a system irrespective of component execution semantics, thus independent of the choice of component models. We have integrated MSL in the ProCom component model with the extension of support for reuse of multi-mode components and distributed mode-switch handling. Although the distributed mode-switch handling of MSL is more flexible and scalable than the conventional centralized approach, when components are deployed on a single hardware platform and global mode information is available, centralized mode-switch handling is more efficient in terms of runtime overhead and mode-switch time. Hence, MSL is supplemented with a mode transformation technique to enhance runtime mode-switch efficiency by converting the distributed mechanism to a centralized mechanism. MSL together with the mode transformation technique has been implemented in a prototype tool where one can build multi-mode systems by reusing multi-mode components. The applicability of MSL is demonstrated in two proof-of-concept case studies.

ISBN 978-91-7485-229-5 ISSN 1651-4238

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Abstract

Self-adaptivity, characterized by the ability to dynamically adjust behavior at runtime, is a growing trend in the evolution of modern embedded systems. While self-adaptive systems tend to be flexible and autonomous, self-adaptivity may inevitably complicate software design, test and analysis. A strategy for taming the growing software complexity of self-adaptive systems is to par-tition system behaviors into different operational modes specified at design time. Such a multi-mode system can change behavior by switching between modes at runtime under certain circumstances. Multi-mode systems can benefit from a complementary approach to the software development of complex sys-tems: Component-Based Software Engineering (CBSE), which fosters reuse of independently developed software components. However, the state-of-the-art component-based development of multi-mode systems does not take full ad-vantage of CBSE, as reuse of modes at component level is barely addressed. Modes are often treated as system properties, while mode switches are han-dled by a global mode manager. This centralized mode management entails global information of all components, whereas the global information may be inaccessible in component-based systems. Another potential problem is that a single mode manager does not scale well, particularly at design time, for a large number of components and modes.

In this thesis we propose a distributed solution to the component-based de-velopment of multi-mode systems, aiming for a more efficient and scalable mode management. Our goal is to fully incorporate modes in software compo-nent reuse, supporting reuse of multi-mode compocompo-nents, i.e., compocompo-nents able to run in multiple modes. We have developed a generic framework, the Mode-Switch Logic (MSL), which not only supports reuse of multi-mode compo-nents but also provides runtime mechanisms for handling mode switch. MSL includes three fundamental elements: (1) a mode-aware component model with the formal specification of reusable multi-mode software components; (2) a

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Abstract

Self-adaptivity, characterized by the ability to dynamically adjust behavior at runtime, is a growing trend in the evolution of modern embedded systems. While self-adaptive systems tend to be flexible and autonomous, self-adaptivity may inevitably complicate software design, test and analysis. A strategy for taming the growing software complexity of self-adaptive systems is to par-tition system behaviors into different operational modes specified at design time. Such a multi-mode system can change behavior by switching between modes at runtime under certain circumstances. Multi-mode systems can benefit from a complementary approach to the software development of complex sys-tems: Component-Based Software Engineering (CBSE), which fosters reuse of independently developed software components. However, the state-of-the-art component-based development of multi-mode systems does not take full ad-vantage of CBSE, as reuse of modes at component level is barely addressed. Modes are often treated as system properties, while mode switches are han-dled by a global mode manager. This centralized mode management entails global information of all components, whereas the global information may be inaccessible in component-based systems. Another potential problem is that a single mode manager does not scale well, particularly at design time, for a large number of components and modes.

In this thesis we propose a distributed solution to the component-based de-velopment of multi-mode systems, aiming for a more efficient and scalable mode management. Our goal is to fully incorporate modes in software compo-nent reuse, supporting reuse of multi-mode compocompo-nents, i.e., compocompo-nents able to run in multiple modes. We have developed a generic framework, the Mode-Switch Logic (MSL), which not only supports reuse of multi-mode compo-nents but also provides runtime mechanisms for handling mode switch. MSL includes three fundamental elements: (1) a mode-aware component model with the formal specification of reusable multi-mode software components; (2) a

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IV

mode mapping mechanism for the seamless composition of multi-mode com-ponents; and (3) a mode-switch runtime mechanism which is executed by each component in isolation from its functional execution and coordinates the mode switches of different components without the need of global mode information. The mode-switch runtime mechanism has been verified by model checking in conjunction with mathematical proofs. We also provide a mode-switch timing analysis for the runtime mechanism to respect real-time requirements.

MSL is dedicated to the mode aspect of a system irrespective of component execution semantics, thus independent of the choice of component models. We have integrated MSL in the ProCom component model with the extension of support for reuse of multi-mode components and distributed mode-switch han-dling. Although the distributed mode-switch handling of MSL is more flexible and scalable than the conventional centralized approach, when components are deployed on a single hardware platform and global mode information is avail-able, centralized mode-switch handling is more efficient in terms of runtime overhead and mode-switch time. Hence, MSL is supplemented with a mode transformation technique to enhance runtime mode-switch efficiency by con-verting the distributed mechanism to a centralized mechanism. MSL together with the mode transformation technique has been implemented in a prototype tool where one can build multi-mode systems by reusing multi-mode compo-nents. The applicability of MSL is demonstrated in two proof-of-concept case studies.

Populärvetenskaplig

sammanfattning

Vi omges dagligen av datorsystem som är inbyggda i produkter—så kallade in-byggda system. De finns i allt från smarta telefoner, medicinska apparater och industrirobotar till bilar och flygplan. Moderna inbyggda system blir alltmer anpassningsbara, med förmåga att dynamiskt anpassa sitt beteende på begäran eller när operativa förhållanden ändras. Anpassningsbara system är vanligtvis flexibla och autonoma, men som sidoeffekt kan de komplicera mjukvarudesig-nen, liksom testning och analys.

En effektiv metod för att hantera ökad komplexitet i programvaran av an-passningbara system är att dela upp systemet i olika driftlägen. Systemet kan då byta beteenden genom att växla mellan olika driftlägen. Till exempel kan programvaran som styr ett flygplan vara uppdelad i driftlägena taxi, start, flyg och landning. System med multipla driftlägen kan utnyttja en kompletterande teknik för programvaruutveckling av komplexa system: komponentbaserad programvaruutveckling som bygger på återanvändning av tidigare utvecklade programvarukomponenter. Det finns redan komponentbaserade tekniker som använder en centraliserad hantering av driftlägesväxlingar, en av de absolut viktigaste frågorna i system med multipla driftlägen. Men tyvärr är en cen-traliserad driftlägeshantering inte skalbar och därför olämplig att använda i mer komplexa system.

Vi har utvecklat ett ramverk, Mode-Switch Logic (MSL), som inte bara stödjer återanvändning av komponenter som kan hantera multipla driftlägen, utan också innehåller stöd för att genomföra driftväxling. Till skillnad från centraliserad driftväxling, hanteras MSLs driftväxling av en lokal algoritm som implementerar såväl den egna driftväxlingen som samordningen med driftväxling i andra komponenter. Vi har dessutom utvecklat en analysmetod

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IV

mode mapping mechanism for the seamless composition of multi-mode com-ponents; and (3) a mode-switch runtime mechanism which is executed by each component in isolation from its functional execution and coordinates the mode switches of different components without the need of global mode information. The mode-switch runtime mechanism has been verified by model checking in conjunction with mathematical proofs. We also provide a mode-switch timing analysis for the runtime mechanism to respect real-time requirements.

MSL is dedicated to the mode aspect of a system irrespective of component execution semantics, thus independent of the choice of component models. We have integrated MSL in the ProCom component model with the extension of support for reuse of multi-mode components and distributed mode-switch han-dling. Although the distributed mode-switch handling of MSL is more flexible and scalable than the conventional centralized approach, when components are deployed on a single hardware platform and global mode information is avail-able, centralized mode-switch handling is more efficient in terms of runtime overhead and mode-switch time. Hence, MSL is supplemented with a mode transformation technique to enhance runtime mode-switch efficiency by con-verting the distributed mechanism to a centralized mechanism. MSL together with the mode transformation technique has been implemented in a prototype tool where one can build multi-mode systems by reusing multi-mode compo-nents. The applicability of MSL is demonstrated in two proof-of-concept case studies.

Populärvetenskaplig

sammanfattning

Vi omges dagligen av datorsystem som är inbyggda i produkter—så kallade in-byggda system. De finns i allt från smarta telefoner, medicinska apparater och industrirobotar till bilar och flygplan. Moderna inbyggda system blir alltmer anpassningsbara, med förmåga att dynamiskt anpassa sitt beteende på begäran eller när operativa förhållanden ändras. Anpassningsbara system är vanligtvis flexibla och autonoma, men som sidoeffekt kan de komplicera mjukvarudesig-nen, liksom testning och analys.

En effektiv metod för att hantera ökad komplexitet i programvaran av an-passningbara system är att dela upp systemet i olika driftlägen. Systemet kan då byta beteenden genom att växla mellan olika driftlägen. Till exempel kan programvaran som styr ett flygplan vara uppdelad i driftlägena taxi, start, flyg och landning. System med multipla driftlägen kan utnyttja en kompletterande teknik för programvaruutveckling av komplexa system: komponentbaserad programvaruutveckling som bygger på återanvändning av tidigare utvecklade programvarukomponenter. Det finns redan komponentbaserade tekniker som använder en centraliserad hantering av driftlägesväxlingar, en av de absolut viktigaste frågorna i system med multipla driftlägen. Men tyvärr är en cen-traliserad driftlägeshantering inte skalbar och därför olämplig att använda i mer komplexa system.

Vi har utvecklat ett ramverk, Mode-Switch Logic (MSL), som inte bara stödjer återanvändning av komponenter som kan hantera multipla driftlägen, utan också innehåller stöd för att genomföra driftväxling. Till skillnad från centraliserad driftväxling, hanteras MSLs driftväxling av en lokal algoritm som implementerar såväl den egna driftväxlingen som samordningen med driftväxling i andra komponenter. Vi har dessutom utvecklat en analysmetod

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VI

för att räkna ut hur lång tid det tar att genomföra driftväxling.

MSL är ett generiskt ramverk som kan anpassas till olika komponentmod-eller. Vi har integrerat MSL i komponentmodellen ProCom, som därmed utökats med stöd för återanvändning av komponenter med multipla driftlä-gen och distribuerad hantering av driftväxling. MSL har även implementer-ats i ett prototypverktyg som utöver att erbjuda en koppling mellan MSL och den kommersiella komponentmodellen Rubus också implementerar en mapp-ning av MSLs flexibla driftlägeshantering till Rubus centraliserade hantering. Mappningen visar hur MSLs flexibilitet kan kombineras med effektiviteten hos centraliserad driftlägeshantering. Slutligen har vi demonstrerat användningen av MSL i två fallstudier.

摘

摘要

要

嵌入式系统在日常生活中无处不在。比如智能手机，医疗器械，工业机器人，汽车，飞机等等都属于嵌入式系统。越来越多的嵌入式系统正在逐渐发展成为具有自适应性的系统。自适应性使得一个系统能够实时动态改变自身行为和功能来适应用户的手动调整和运行环境的改变。自适应系统较为灵活和自治，但容易导致更加复杂的软件设计，测试和分析。在系统设计阶段将系统功能划分为多个运行模式是一个有效的处理自适应系统软件复杂度的方法。多模式系统可以在特定情况下实时切换模式来改变运行功能。例如飞机的控制软件通常可以运行地面滑行模式，起飞模式，飞行模式，和降落模式等等。多模式系统的开发还能额外受益于基于组件的软件工程。基于组件的软件工程是另一个有效管理复杂软件的方法。其特色在于重复使用独立开发的软件组件。现有的基于组件的软件开发技术对于多模式系统而言并没有将基于组件的软件工程的优势充分利用起来。组件的模式在组件重用中很少被提及。处理模式转换是多模式系统最重要的问题之一。现有的方法通常使用一个全局模式管理器来处理模式转换。这样的集中式模式管理可扩展性不够理想，从而不适合构建较为复杂的系统。本论文中我们提出一个集散式的方法来实现对多模式系统的基于组件的开发。和其它方法相比，这种集散式的方法具有更好的可扩展性，并且能够更为有效的管理组件和系统模式。我们将组件模式完全整合到软件组件重用中，支持多模式组件的可重用(多模式组件即为可以运行多个模式的组件_{)。这种集散式的开发方法被称为模式转换逻辑 (MSL:} Mode-Switch Logic)。MSL不仅支持多模式组件的可重用，而且提供一系列算法来有效处理模式转换。这些算法运行在每一个组件里并且协调不同组件的模式转换。此外，我们对模式转换进行时间分析，计算模式转换所需时间，保证模式转换及时完成和满足系统的实时要求。 MSL对于组件模型的选择没有特别要求，适用于很多不同的组件模型。我们已经将MSL应用到ProCom组件模型，使得ProCom支持多模式 VII

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VI

för att räkna ut hur lång tid det tar att genomföra driftväxling.

MSL är ett generiskt ramverk som kan anpassas till olika komponentmod-eller. Vi har integrerat MSL i komponentmodellen ProCom, som därmed utökats med stöd för återanvändning av komponenter med multipla driftlä-gen och distribuerad hantering av driftväxling. MSL har även implementer-ats i ett prototypverktyg som utöver att erbjuda en koppling mellan MSL och den kommersiella komponentmodellen Rubus också implementerar en mapp-ning av MSLs flexibla driftlägeshantering till Rubus centraliserade hantering. Mappningen visar hur MSLs flexibilitet kan kombineras med effektiviteten hos centraliserad driftlägeshantering. Slutligen har vi demonstrerat användningen av MSL i två fallstudier.

摘

摘要

要

嵌入式系统在日常生活中无处不在。比如智能手机，医疗器械，工业机器人，汽车，飞机等等都属于嵌入式系统。越来越多的嵌入式系统正在逐渐发展成为具有自适应性的系统。自适应性使得一个系统能够实时动态改变自身行为和功能来适应用户的手动调整和运行环境的改变。自适应系统较为灵活和自治，但容易导致更加复杂的软件设计，测试和分析。在系统设计阶段将系统功能划分为多个运行模式是一个有效的处理自适应系统软件复杂度的方法。多模式系统可以在特定情况下实时切换模式来改变运行功能。例如飞机的控制软件通常可以运行地面滑行模式，起飞模式，飞行模式，和降落模式等等。多模式系统的开发还能额外受益于基于组件的软件工程。基于组件的软件工程是另一个有效管理复杂软件的方法。其特色在于重复使用独立开发的软件组件。现有的基于组件的软件开发技术对于多模式系统而言并没有将基于组件的软件工程的优势充分利用起来。组件的模式在组件重用中很少被提及。处理模式转换是多模式系统最重要的问题之一。现有的方法通常使用一个全局模式管理器来处理模式转换。这样的集中式模式管理可扩展性不够理想，从而不适合构建较为复杂的系统。本论文中我们提出一个集散式的方法来实现对多模式系统的基于组件的开发。和其它方法相比，这种集散式的方法具有更好的可扩展性，并且能够更为有效的管理组件和系统模式。我们将组件模式完全整合到软件组件重用中，支持多模式组件的可重用(多模式组件即为可以运行多个模式的组件_{)。这种集散式的开发方法被称为模式转换逻辑 (MSL:} Mode-Switch Logic)。MSL不仅支持多模式组件的可重用，而且提供一系列算法来有效处理模式转换。这些算法运行在每一个组件里并且协调不同组件的模式转换。此外，我们对模式转换进行时间分析，计算模式转换所需时间，保证模式转换及时完成和满足系统的实时要求。 MSL对于组件模型的选择没有特别要求，适用于很多不同的组件模型。我们已经将MSL应用到ProCom组件模型，使得ProCom支持多模式 VII

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VIII

组件的可重用和集散式的模式转换处理。目前我们已经在一款正在开发

的工具中实现了_{MSL的一些主要功能。该工具为多模式组件的重用提供}

了一个开发平台。_{MSL的实用性在本论文中通过两个案例被演示出来。}

Acknowledgements

What can be experienced and achieved over a half-decade? Apparently, a vast number of things could come to mind, developing a better career, learning a new language, acquiring new skills, writing a book, building a family, traveling around the world, experience new cultures, making new friends...you name it. In retrospect, I am truly proud of the most splendid episode of my life over the last five years—the odyssey to a PhD! While doing research as a PhD student is deemed to be dreary and tedious in the eyes of some other people, it is one of the coolest vocations that I could anticipate. Before I was enrolled as a PhD student at Mälardalen University (MDH), attaining a PhD degree seemed like an insurmountable mission for me. Yet I am fortunate enough to come this far, ready for the defense and on the verge of accomplishing the mission. This would certainly not have been possible without the help and support of those fantastic people that I ever met during my PhD studies.

My deepest gratitude undoubtedly goes to my main supervisor Hans Hans-son who guided and inspired me all the way to the end of my PhD journey. Thank you for leading me along the path from a fresh student innocent of the profound academic world to an independent researcher! You are not only a mentor for me but also an academic superstar I respect from the bottom of my heart. I would also like to express my immense appreciation to my co-supervisors Paul Pettersson and Thomas Nolte. You have helped me and in-fluenced me in various ways since my first year in Västerås. I am always encouraged by your wisdom, charisma, and professional attitude.

Life is accompanied by decision making all the time. Starting a PhD in Sweden is probably the best decision that I have ever made. Another decision which is equally sensible is moving to Sweden in the summer of 2008. Sweden is a wonderful country. The longer I stay here, the more affection accumulates. I am sincerely grateful to Damir Isovic, without whom I would have never thought of going abroad. Your visit to East China University of Science and Technology (ECUST, my home university in China) in 2007 is a blessing for

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VIII

组件的可重用和集散式的模式转换处理。目前我们已经在一款正在开发

的工具中实现了_{MSL的一些主要功能。该工具为多模式组件的重用提供}

了一个开发平台。_{MSL的实用性在本论文中通过两个案例被演示出来。}

Acknowledgements

What can be experienced and achieved over a half-decade? Apparently, a vast number of things could come to mind, developing a better career, learning a new language, acquiring new skills, writing a book, building a family, traveling around the world, experience new cultures, making new friends...you name it. In retrospect, I am truly proud of the most splendid episode of my life over the last five years—the odyssey to a PhD! While doing research as a PhD student is deemed to be dreary and tedious in the eyes of some other people, it is one of the coolest vocations that I could anticipate. Before I was enrolled as a PhD student at Mälardalen University (MDH), attaining a PhD degree seemed like an insurmountable mission for me. Yet I am fortunate enough to come this far, ready for the defense and on the verge of accomplishing the mission. This would certainly not have been possible without the help and support of those fantastic people that I ever met during my PhD studies.

My deepest gratitude undoubtedly goes to my main supervisor Hans Hans-son who guided and inspired me all the way to the end of my PhD journey. Thank you for leading me along the path from a fresh student innocent of the profound academic world to an independent researcher! You are not only a mentor for me but also an academic superstar I respect from the bottom of my heart. I would also like to express my immense appreciation to my co-supervisors Paul Pettersson and Thomas Nolte. You have helped me and in-fluenced me in various ways since my first year in Västerås. I am always encouraged by your wisdom, charisma, and professional attitude.

Life is accompanied by decision making all the time. Starting a PhD in Sweden is probably the best decision that I have ever made. Another decision which is equally sensible is moving to Sweden in the summer of 2008. Sweden is a wonderful country. The longer I stay here, the more affection accumulates. I am sincerely grateful to Damir Isovic, without whom I would have never thought of going abroad. Your visit to East China University of Science and Technology (ECUST, my home university in China) in 2007 is a blessing for

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me, as it sets up the initial bridge between China and Sweden right in front of me. Many thanks also go to Huifeng Wang, my ex-supervisor at ECUST, who encouraged my overseas study at MDH.

Apart from my supervisors, there are many other people who ever offered technical advice at different stages of my PhD studies. I convey my heart-felt thanks to Tomas Bures for being the opponent for my Licentiate semi-nar, Sasikumar Punnekkat for being the examiner for my Licentiate semisemi-nar, Mikael Sjödin for being the examiner for my Licentiate proposal, and Cristina Seceleanu for being the examiner for my PhD proposal. I am deeply indebted to Jan Carlson who has invariably been a reliable source for consultation not only on CBSE, ProCom, and UML metamodels, but also on the technical de-tails of my own research. Thank you for your great contributions to the fruitful discussions and the papers that we co-authored! Another person that merits my wholehearted gratitude is Etienne Borde, who actively guided me after I just started my PhD journey. Another thanks goes to Paul Pettersson and Cristina Seceleanu for enlightening me about formal verification in my research. In ad-dition, I would like to acknowledge Barbara Gallina and Björn Lisper for the advice beneficial to my research.

During the last year of my PhD studies, with the intention of exploring the industrial value of our research results, I visited Arcticus Systems AB several times and received generous support from Kurt Lundbäck and John Lundbäck, the founders of the Rubus component model. My warmest appreciation to you both! Moreover, many thanks go to Kaj Hänninen, Saad Mubeen and Mikael Sjödin for helping me gain so much insight into Rubus.

I used to have a tough time with UPPAAL modeling and verification. UP-PAAL is an excellent tool, however, due to my complex models, the verification turned out to be so computationally expensive and memory-demanding that I became desperate for additional hardware assistance. I would like to thank Daniel Flemström for giving me remote access to MDH-Ericsson lab, Mah-naz Malekzadeh and Irfan Sljivo for sharing a workstation that completed my experiments in time.

The completion of a PhD betokens the commencement of a brand new ca-reer. It is my absolute honor to be accepted as a postdoc at Chalmers University of Technology (CTH) before my PhD degree is completed. My special thanks goes to Christian Berger and Michel Chaudron. Thank you for believing in me and providing me with such a superb opportunity to work on self-driving vehi-cles! Christian, even though I have not started my official employment in your team, I have been truly impressed by your devotion to research and passion for coding. It would be really exciting to work with you soon! Another special

XI thanks is dedicated to Ivica Crnkovic not only for his recommendation for my postdoc application but also for all the great times that he brought to me. Thank you for taking me to the magnificent CBSE community, taking good care of me during conference trips, and getting me involved in organizing ASE’14! It is a pity that I did not have a chance to work with you at MDH, but what a privilege it is to join your research group at CTH as a postdoc!

Since the end of 2014, I joined a local postdoc mentorship program to gain a preliminary understanding of the essentials for a postdoc. I warmly thank Wasif Afzal for arranging such an informative program. In particular, I am beholden to Kristina Lundqvist, my mentor in this program. Thank you for your guidance, encouragement, and genuine support for my job seeking!

My research has been accompanied by a variety of PhD courses that cover a broad spectrum of topics and have significantly enriched my knowledge and mindset. I would like to express my sincere gratitude to those who ever contributed to these courses, including (but not limited to) Gordana Dodig-Crnkovic, Jan Gustafsson, Lars Asplund, Cristina Seceleanu, Paul Pettersson, Hans Hansson, Thomas Nolte, Emma Nehrenheim, Ivica Crnkovic, Séverine Sentilles, Aneta Vulgarakis, Iain Bate, Sasikumar Punnekkat, Phil McMim, Ri-cardo J. Rodríguez, Reinder J. Bril, Hongyu Pei Breivold, Moris Behnam, Seif Haridi, Elisabeth Uhlemann, Lucia Lo Bello, Mats Björkman, Luis Almeida, Maria Lindén, and Johan Åkerberg.

In 2014, I received a kind invitation from Thomas Nolte to join the pow-erful CORE (Complex Real-Time Embedded Systems) research group. A big thank you to all the past and current CORE members, including (but not limited to) Thomas Nolte, Moris Behnam, Mohammad Ashjaei, Sara Afshar, Nima Moghaddami Khalilzad, Meng Liu, Saad Mubeen, Matthias Becker, Hamid Reza Faragardi, Reinder J. Bril, Luis Almeida, Rafia Inam, Mikael Åsberg, Yue Lu, and Farhang Nemati. Moris, thank you again for all the help and for being such a nice neighbor next to my office over these years!

The school of Innovation, design and engineering (IDT) at MDH, which I belong to, is a harmonious international family. We have colleagues from different countries with different cultural backgrounds, speaking different lan-guages. Your kindness makes me enjoy every single working day. I am gonna miss all the happy moments with you during conference trips, coffee beaks, lunch chats, parties, and departmental social activities! In addition to the afore-mentioned thank lists, my warmest appreciation goes to (in alphabetical order): Abhilash Thekkilakattil, Abu Naser Masud, Adnan Causevic, Aida Causevic, Alessio Bucaioni, Andreas Gustavsson, Andreas Hjertström, Andreas Johnsen, Antonio Cicchetti, Baran Cürüklü, Batu Akan, Dag Nyström, Daniel Kade,

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