introduction/introduction.tex

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   3 \begin{document}
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   7 \chapter{Introduction}%
   8 %\setlength{\epigraphwidth}{.5\textwidth}%
   9 %\epigraphhead[30]{
  10 %       A \textbf{rhapsody} in music is a one-movement work that is episodic yet integrated, free-flowing in structure, featuring a range of highly contrasted moods, colour, and tonality. An air of spontaneous inspiration and a sense of improvisation make it freer in form than a set of variations.
  11 %}{%
  12 %       Wikipedia~\cite{wikipedia_contributors_rhapsody_2022}
  13 %}%
  14 \label{chp:introduction}
  15 The sheer number of connected devices around us is increasing exponentially.
  16 First and foremost, these devices are driven by software.
  17 This thesis is about \ldots
  18 \todo[inline]{introduction}
  19
  20 \section{Internet of Things}
  21 \todo[inline]{add more citations and rewrite to make modern}
  22 The \gls{IOT} is growing rapidly and it is changing the way people and machines interact with the world.
  23 While the term \gls{IOT} briefly gained interest around 1999 to describe the communication of \gls{RFID} devices~\todo{cite}, it probably already popped up halfway the eigthies in a speech by Peter T. Lewis~\cite{peter_t_lewis_speech_1985}.
  24
  25 \begin{quote}
  26         The \acrlong{IOT}, or \acrshort{IOT}, is the integration of people, processes and technology with connectable devices and sensors to enable remote monitoring, status, manipulation and evaluation of trends of such devices.
  27 \end{quote}
  28
  29 CISCO states that the \gls{IOT} only started when there where as many connected devices as there were people on the globe, i.e.\ around 2008~\cite{evans_internet_2011}.
  30 Today, the \gls{IOT} is the term for a system of devices that sense the environment, act upon it and communicate with each other and the world.
  31 These connected devices are already in everyone's household in the form of smart electricity meters, smart fridges, smartphones, smart watches, home automation, \etc.
  32
  33 When describing \gls{IOT} systems, a layered, or tiered architecture is often used to compartmentalize the technology.
  34 The number of tiers heavily depends on the complexity of the model but for the intents and purposes of the thesis, the four layer architecture shown in \cref{fig:iot-layers} is used.
  35
  36 \begin{figure}[ht]
  37         \centering
  38         \includestandalone{iot-layers}
  39         \caption{The four layered \gls{IOT} architecture.}%
  40         \label{fig:iot-layers}
  41 \end{figure}
  42
  43 \begin{description}
  44         \item[Presentation layer] This presentation layer provides the interface between the user and the \gls{IOT} application.
  45                 For example, in home automation, this is often implemented as a web interface or a mobile app.
  46         \item[Application layer]
  47                 Servers often power the application layer, by providing the data storage,
  48                 One of its goals is to provide the \gls{API}, interfaces and data storage
  49         \item[Network layer] connects all layers together.
  50                 In many applications this may be implemented using conventional networking techniques such as WiFi or wire networks.
  51                 However, recently, networks tailored to the needs of \gls{IOT} applications have been increasingly popular such as \gls{BLE}, LoRa, ZigBee or LTE-M.
  52         \item[Perception layer], also called edge layer, collects the data, interacts with the environment and consists of (edge) devices equipped with various sensors and actuators.
  53                 As a special type of device, it may also contain a \gls{SN}.
  54                 A \gls{SN} is a collection of sensors connected by a mesh network or central hub.
  55 \end{description}
  56
  57 While the number of devices seems to be growing exponentially fast, programming \gls{IOT} systems remains difficult as there is a lot of semantic friction~\cite{ireland_classification_2009}.
  58
  59 The devices are a large heterogeneous collection of different platforms, protocols and languages resulting in impedance problems or semantic friction between layers~\cite{ireland_classification_2009}.
  60
  61 Additionaly, the perception layer often is a heterogeneous collections of microcontrollers as well, each having their own peculiarities, language of choice and hardware interfaces.
  62 The hardware needs to be cheap, small-scale and energy efficient.
  63 As a result, the \glspl{MCU} used to power these devices do not have a lot of computational power, a soup\c{c}on of memory, and little communication bandwidth.
  64 Typically the devices do not run a full fledged \gls{OS} but a compiled firmware.
  65 This firmware is often written in an imperative language that needs to be flashed to the program memory.
  66 It is possible to dynamically send the program to the program memory using \gls{OTA} programming~\cite{baccelli_scripting_2018,baccelli_reprogramming_2018}.
  67 Program memory typically is flash based and only lasts a couple of thousand writes before it wears out.
  68 While devices are getting a bit faster, smaller, and cheaper, they keep these properties to an extent.
  69 The properties of the device greatly reduce the flexibility for dynamic systems where tasks are created on the fly, executed on demand and require parallel execution.
  70 These problems can be mitigated by dynamically sending code to be interpreted to the \gls{MCU}.
  71 With interpretation, a specialized interpreter is flashed in the program memory once that receives the program code to execute at runtime.
  72
  73 %weiser_computer_1991
  74 \section{Domain-specific languages}
  75 % General
  76 Programming languages can be divided up into two categories: \glspl{DSL} and \glspl{GPL}~\cite{fowler_domain_2010}.
  77 Where \glspl{GPL} are not made with a demarcated area in mind, \glspl{DSL} are tailor-made for a specific domain.
  78 Writing idiomatic domain-specific code in an \gls{DSL} is easy but this may come at the cost of the \gls{DSL} being less expressive to an extent that it may not even be Turing complete.
  79 \Glspl{DSL} come in two main flavours: standalone and embedded\footnote{Also called external and internal respectively.} of which \glspl{EDSL} can again be classified into heterogeneous and homogeneous languages (see \cref{fig:hyponymy_of_dsls} for this hyponymy).
  80
  81 \begin{figure}[ht]
  82         \centering
  83         \includestandalone{hyponymy_of_dsls}
  84         \caption{Hyponymy of \glspl{DSL} (adapted from~\cite[pg.\ 2]{mernik_extensible_2013})}%
  85         \label{fig:hyponymy_of_dsls}
  86 \end{figure}
  87
  88 \glspl{DSL} where historically created as standalone languages which means all the machinery is developed solely for the language.
  89 The advantage of this approach is that the language designer is free to define the syntax and type system of the language as they wish, not being restricted by any constraint.
  90 Unfortunately it also means that they need to develop a compiler or interpreter for the language to be usable making standalone \glspl{DSL} costly to create.
  91 Examples of standalone \glspl{DSL} are regular expressions, make, yacc, XML, SQL, \etc.
  92
  93 A radically different approach is embeddding the \gls{DSL} in a host language, i.e.\ \glspl{EDSL}~\cite{hudak_modular_1998}.
  94 By defining the language as constructs in the host language, much of the machinery is inherited and the cost of creating embedded languages is very low.
  95 There are however two sides to the this coin.
  96 If the syntax of the host language is not very flexible, the syntax of the \gls{DSL} may become clumsy.
  97 Furthermore, errors shown to the programmer may be larded with host language errors, making it difficult for a non-expert of the host language to work with the \gls{DSL}.
  98
  99 Tratt applied a notion from metaprogramming~\cite{sheard_accomplishments_2001} to \glspl{EDSL} to define homogeneity and heterogeneity of \glspl{EDSL} as follows~\cite{tratt_domain_2008}:
 100 \begin{quote}
 101         a homogeneous system is one where all the components are specifically designed to work with each other, whereas in heterogeneous systems at least one of the components is largely, or completely, ignorant of the existence of the other parts of the system.
 102 \end{quote}
 103 Homogeneous \glspl{EDSL} are therefore languages that are solely defined as an extension to their host language.
 104 They often restrict features of the host language to provide a safer interface or capture an idiomatic pattern in the host language for reuse.
 105 The difference between a library and a homogeneous \glspl{EDSL} is not always clear.
 106 Examples of homogeneous \glspl{EDSL} are libraries such as ones for \glspl{GUI} creation, LISP's macro system, \etc.
 107
 108 On the other hand, heterogeneous \glspl{EDSL} are languages that are not executed in the host language.
 109 For example, Elliott et al.\ describe the language Pan, for which the final representation in the host language is a compiler that will, when executed, generate code for a completely different target platform~\cite{elliott_compiling_2003}.
 110 In fact, \gls{ITASK} and \gls{MTASK} are both heterogeneous \glspl{EDSL}.
 111
 112 \section{Functional programming}\label{ssec:functional programming}
 113 \Gls{FP} is \ldots
 114 \Gls{FP} languages are naturally suitable as a host language for \gls{DSL} embedding because of their rich type systems and minimal and extensible syntax~\cite{gibbons_functional_2015}.
 115
 116 \section{Task-oriented programming}
 117 \Gls{TOP} is a declarative programming paradigm designed to model interactive systems~\cite{plasmeijer_task-oriented_2012}.
 118 Instead of dividing problems into layers or tiers, as is done in \gls{IOT} architectures as well, it deals with separation of concerns in a novel way.
 119 From the data types, utilising various \emph{type-parametrised} concepts, all other aspects are handled (see \cref{fig:tosd}).
 120 This approach to software development is also called \gls{TOSD}~\cite{wang_maintaining_2018}.
 121
 122 \begin{figure}[ht]
 123         \centering
 124         \begin{subfigure}[t]{.5\textwidth}
 125                 \centering
 126                 \includestandalone{traditional}
 127                 \caption{Traditional layered approach.}
 128         \end{subfigure}%
 129         \begin{subfigure}[t]{.5\textwidth}
 130                 \centering
 131                 \includestandalone{tosd}
 132                 \caption{\Gls{TOSD} approach.}
 133         \end{subfigure}
 134         \caption{Separation of concerns in a traditional setting and in \gls{TOSD} (adapted from~\cite[pg.\ 20]{wang_maintaining_2018}).}%
 135         \label{fig:tosd}
 136 \end{figure}
 137
 138 \begin{description}
 139         \item[Presentation layer: UI]
 140                 The \gls{UI} of the system is automatically generated from the representation of the type.
 141                 For instance, \gls{TOP} languages implemented in an \gls{FP} language often use generic programming or template metaprogramming to automatically achieve this.
 142                 \Gls{TOP} languages embedded in imperative programming languages may use introspection\todo{Do I want this sentence here?}.
 143                 Even though the \gls{UI} is generated from the structure of the datatypes, in many practical \gls{TOP} systems it can be tweaked afterwards to suit the specific needs of the application.
 144         \item[Business layer: Tasks]
 145                 A task is an abstract representation of a piece of work that needs to be done.
 146                 It provides an intuitive abstraction over work in the real world.
 147                 Just as with real-life tasks and workflow, tasks can be combined in various ways such as in parallel or in sequence.
 148                 Furthermore, tasks are observable which means it is possible to observe a --- partial --- result during execution and act upon it by for example starting new tasks.
 149                 Examples of tasks are filling in a form, sending an email, reading a sensor or even doing a physical task.
 150         \item[Resource access: \glspl{SDS}]
 151                 Tasks can communicate using task values but this imposes a problem in many collaboration patterns where tasks that are not necessarily related need to share data.
 152                 Tasks can also share data using \glspl{SDS}.
 153                 \Glspl{SDS} are an abstraction over any data.
 154                 An \gls{SDS} can represent typed data stored in a file, a chunk of memory, a database \etc.
 155                 \Glspl{SDS} can also represent external impure data such as the time, random numbers or sensory data.
 156                 Similar to tasks, transformation and combination of \glspl{SDS} is possible.
 157         \item[\Gls{UOD}: PL]
 158                 The \gls{UOD} from the business layer is explicitly and separately modelled by the relations that exist in the functions of the host language.
 159                 \gls{TOP} languages are usually embedded in \gls{FP} languages but this not necessarily the case.
 160                 Some host languages also provide the implementations for the tasks and \glspl{SDS}.
 161                 \todo{dit moet beter}
 162 \end{description}
 163
 164 \section{Outline}
 165 %\epigraph{%
 166 %       \textbf{rhapsody} /\textipa{['r\ae{}ps@di]}/ \emph{noun} (pl.\ \textbf{-ies}) a piece of music that is full of feeling and is not regular in form: Liszt's Hungarian Rhapsodies.
 167 %}{%
 168 %       Oxford Advanced Learners Dictionary~\cite{margaret_deuter_rhapsody_2015}.
 169 %}
 170 Wikipedia defines a \emph{rhapsody} as follows~\cite{wikipedia_contributors_rhapsody_2022}:
 171 \begin{quote}
 172         A \textbf{rhapsody} in music is a one-movement work that is episodic yet integrated, free-flowing in structure, featuring a range of highly contrasted moods, colour, and tonality. An air of spontaneous inspiration and a sense of improvisation make it freer in form than a set of variations.
 173 \end{quote}
 174
 175 This thesis follows the tradition and consists of three movements that are episodic yet integrated.
 176 The first movement is about embedded \gls{DSL} techniques, the second movement elaborates on \gls{TOP} for the \gls{IOT} and the third and last movement compares traditional tiered \gls{IOT} architectures to a tierless architectures such as \gls{TOP}.
 177 The movements are readable independently if the reader is familiarised with the background material provided in \cref{chp:introduction}.
 178
 179 \paragraph{\Cref{prt:dsl}} is a cumulative or paper-based movement that focusses on techniques for embedding \glspl{DSL} in functional programming lanugages.
 180 After reading the first chapter, subsequent chapters in this movement are readable as independently.
 181
 182 \subparagraph{\Cref{chp:dsl_embedding_techniques}} shows all the basic techniques and compares the properties.
 183 This chapter is not based on a paper and written as a background for the subsequent chapters in the movement.
 184
 185 \subparagraph{\Cref{chp:classy_deep_embedding}}
 186 This chapter is based on the paper: \emph{Deep Embedding with Class}~\todo[inline]{cite when published}.
 187 During a Master's thesis supervision~\cite{amazonas_cabral_de_andrade_developing_2018}, focussing on an early version of \gls{MTASK}, a seed was planted for a novel deep embedding technique for \glspl{DSL} where the resulting language is extendible both in constructs and in interpretation using type classes and existential data types.
 188 Slowly the ideas organically grew to form the technique shown in the paper.
 189
 190 The research from this paper and writing the paper was solely performed by me.
 191
 192 \subparagraph{\Cref{chp:first-class_datatypes}} shows how to inherit data types in embedded \glspl{DSL} using metaprogramming.
 193 This chapter is based on the paper: \emph{First-Class Data Types in Shallow Embedded Domain-Specific Languages using Metaprogramming}~\todo[inline]{cite when accepted}.
 194
 195 The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman an Rinus Plasmeijer in which we discussed and refined the ideas.
 196
 197 \subparagraph{\Cref{chp:strongly-typed_multi-view_stack-based_computations}} shows how to use advanced \gls{DSL} techniques to embed type safe stack-based computations in a host language.
 198 This chapter is based on the paper: \emph{Strongly-Typed Multi-View Stack-Based Computations}~\todo[inline]{cite when accepted}.
 199
 200 I supported Pieter Koopman in performing the research in this paper.
 201 The paper was mostly written by Pieter Koopman\todo{probably}.
 202
 203 \paragraph{\Cref{prt:top}} is a monograph focussing on \glspl{TOP} for the \gls{IOT}.
 204 Therefore, the chapters depend on eachother and are best read in order.
 205 The monograph is compiled from the following papers and revised lecture notes.
 206
 207 \begin{itemize}
 208         \item \bibentry{koopman_task-based_2018}.
 209         \item \bibentry{lubbers_task_2017} (extension of Master's thesis~\cite{lubbers_task_2018}).
 210         \item \bibentry{lubbers_multitasking_2019}.
 211         \item \emph{Simulation of a Task-Based Embedded Domain Specific Language for the Internet of Things}~\todo[inline]{cite when published}
 212         \item \emph{Writing Internet of Things applications with Task Oriented Programming}~\todo[inline]{cite when published}
 213         \item \bibentry{lubbers_interpreting_2019}.
 214         \item \emph{Reducing the Power Consumption of IoT with Task-Oriented Programming}~\todo[inline]{cite when published} (extensios of Master's thesis by Sjoerd Crooijmans~\cite{crooijmans_reducing_2021}).
 215         \item \emph{Asynchronous Shared Data Sources}~\todo[inline]{cite when accepted}
 216         \item \emph{Green Computing for the Internet of Things}~\todo[inline]{cite when done}
 217         \item \emph{T.B.A.}~\todo[inline]{cite when done}
 218 \end{itemize}
 219
 220 \paragraph{\Cref{prt:tvt}}
 221 This chapter focusses on comparing traditional tiered architectures to tierless architectures and is based on a single journal paper that extensed on a conference paper.
 222 It does both a qualitative and a quantitative four-way comparison of a smart campus application.
 223
 224 The research in these papers and writing them was performed by all authors.
 225 I created the server application, the \gls{CLEAN}/\gls{ITASK}/\gls{MTASK} implementation (\acrshort{CWS}) and the \gls{CLEAN}/\gls{ITASK} implementation (\acrshort{CRS})
 226 Adrian Ramsingh created the micropython implementation (\acrshort{PWS}), the original python implementation (\acrshort{PRS}) and the server application were created by Jeremy Singer, Dejice Jacob and Kristian Hentschel~\cite{hentschel_supersensors:_2016}.
 227
 228 \begin{itemize}
 229         \item \bibentry{lubbers_tiered_2020}.
 230         \item \emph{Could Tierless Languages Reduce IoT Development Grief?}~\todo[inline]{cite when accepted}
 231 \end{itemize}
 232
 233 \paragraph{\Cref{chp:conclusion}} finally concludes and provides an outlook on future work.
 234
 235 \newcounter{secondauthorcnt}
 236 \newcounter{underreviewcnt}
 237 \newcounter{plannedcnt}
 238 \newcounter{publicationscnt}
 239 \newcommand{\secondauthor}{\textsuperscript{$\ast$}\stepcounter{secondauthorcnt}}
 240 \newcommand{\underreview}{\textsuperscript{$\dagger$}\stepcounter{underreviewcnt}}
 241 \newcommand{\planned}{\textsuperscript{$\ddagger$}\stepcounter{plannedcnt}}
 242
 243 \begin{enumerate}
 244         \item \secondauthor{}
 245                 A Task-Based DSL for Microcomputers
 246
 247                 P. Koopman\footnote{\orcid{0000-0002-3688-0957}}, M. Lubbers\footnote{\orcid{0000-0002-4015-4878}}, and R. Plasmeijer (RWDSL 2018)~\cite{koopman_task-based_2018}.
 248         \item Task Oriented Programming and the Internet of Things
 249
 250                 M. Lubbers, P. Koopman, and R. Plasmeijer (IFL 2018)~\cite{lubbers_task_2017} (extension of Master's thesis~\cite{lubbers_task_2018}).
 251         \item Multitasking on Microcontrollers using Task Oriented Programming
 252
 253                 M. Lubbers, P. Koopman, and R. Plasmeijer (MIPRO/4COWS 2019)~\cite{lubbers_multitasking_2019}.
 254         \item \secondauthor{}
 255                 Simulation of a Task-Based Embedded Domain Specific Language for the Internet of Things
 256
 257                 P. Koopman, M. Lubbers, and R. Plasmeijer (CEFP/3COWS 2018).
 258         \item Writing Internet of Things applications with Task Oriented Programming
 259
 260                 M. Lubbers, P. Koopman, and R. Plasmeijer (CEFP/3COWS 2019).
 261         \item Interpreting Task Oriented Programs on Tiny Computers
 262
 263                 M. Lubbers, P. Koopman, and R. Plasmeijer (IFL 2019)~\cite{lubbers_interpreting_2019}.
 264         \item Tiered versus Tierless IoT Stacks: Comparing Smart Campus Software Architectures
 265
 266                 M. Lubbers, P. Koopman, A. Ramsingh\footnote{\orcid{0000-0003-3501-902X}}, J. Singer\footnote{\orcid{0000-0001-9462-6802}}, and P. Trinder\footnote{\orcid{0000-0003-0190-7010}} (IoT 2020)~\cite{lubbers_tiered_2020}.
 267
 268         % in press
 269         \item Deep Embedding with Class
 270
 271                 M. Lubbers (TFP 2022).
 272         \item \secondauthor{}
 273                 Reducing the Power Consumption of IoT with Task-Oriented Programming
 274
 275                 S. Crooijmans, M. Lubbers, and P. Koopman (TFP 2022).
 276
 277         %Under review
 278         \item \underreview{} Could Tierless Languages Reduce IoT Development Grief?
 279
 280                 M. Lubbers, P. Koopman, A. Ramsingh, J. Singer, and P. Trinder (ACM TIOT) (extension of~\cite{lubbers_tiered_2020}).
 281         \item \secondauthor\underreview{}
 282                 Strongly-Typed Multi-View Stack-Based Computations
 283
 284                 M. Lubbers and P. Koopman (IFL 2022 under review).
 285         \item \underreview{} First-Class Data Types in Shallow Embedded Domain-Specific Languages using Metaprogramming
 286
 287                 M. Lubbers, P. Koopman, and R. Plasmeijer (IFL 2022 under review).
 288         \item \underreview{} Asynchronous Shared Data Sources
 289
 290                 M. Lubbers, H. Böhm, P. Koopman, and R. Plasmeijer (IFL 2022 under review).
 291
 292         %Planned
 293         \item \planned{} Green Computing for the Internet of Things
 294
 295                 M. Lubbers, P. Koopman (Sustrainable 2022 planned).
 296         \item \planned{} T.B.A.
 297
 298                 M. Lubbers, P. Koopman (Sustrainable 2023 planned).
 299
 300                 \setcounter{publicationscnt}{\value{enumi}}
 301 \end{enumerate}
 302
 303 There are \thepublicationscnt{} publications of which \thesecondauthorcnt{} I'm second author, \theunderreviewcnt{} are under review and \theplannedcnt{} are planned.
 304
 305 \input{subfilepostamble}
 306 \end{document}