intro/intro.tex

   1 \documentclass[../thesis.tex]{subfiles}
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   3 \input{subfilepreamble}
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   5 \begin{document}
   6 \chapter{Prelude}%
   7 \label{chp:introduction}
   8 In 2022, there were an estimated number of 13.4 billion of connected computers that sense, act or otherwise interact with people, other computers and the physical world surrounding us\footnote{\url{https://transformainsights.com/research/tam/market}, accessed on: \formatdate{13}{10}{2022}}.
   9 The variety among these devices is considerable but these devices have one thing in common though: they are all controlled by software.
  10 Concretely this means that programmers write code for these specific device to make sure the brains of the device---the processor---do what we want it to do.
  11
  12 An increasing amount of these connected devices are so-called \emph{edge devices} that operate in the \gls{IOT}.
  13 Typically these edge devices are small microprocessors containing various sensors and actuators to interact with the physical world.
  14 They are often part of and coordinated by a bigger system called \gls{IOT} systems.
  15 The variety among the edge devices and the fact that they differ substantially from other devices makes it complex to program \gls{IOT} systems.
  16
  17 %These ed
  18 %These edge devices differ very much from other devices we see around us.
  19 %Compared to servers, laptops, tablets, or mobile phones they boast tiny amounts of memory, are powered by a slow but energy efficient microprocessor, only support low-level programming languages, and are not so easily reprogrammed.
  20 %Moreover, these edge devices differ among eachother as well by using various microprocessor architectures, different communication protocols and using a variety of device-specific toolchains.
  21 %As a result, there are many points of failure and programming these systems is difficult and error-prone.
  22 %
  23 %\Gls{TOP} is a novel programming paradigm that offers a solution to this problem.
  24 %In a \gls{TOP} language, from a single declarative specification of the work that needs to be done, ready-for-work applications are generated for all layers of the system.
  25 %However, the hardware requirements for traditional \gls{TOP} frameworks make it not feasable to run these generated applications on resource-constrained edge devices.
  26 %
  27 %\Glspl{DSL} can overcome this limitation because domain-specific knowledge is built into the programming language, allowing for lower hardware requirements.
  28 %This thesis presents \gls{MTASK}, a \gls{TOP} \gls{DSL} for edge devices that can be fully integrated with \gls{ITASK}, a \gls{TOP} \gls{DSL} for distributed multi-user workflow systems.
  29 %With \gls{MTASK}, all layers of an \gls{IOT} system can be programmed from a single programming language in a single programming paradigm.
  30
  31 \section{Internet of things}\label{sec:back_iot}
  32 The \gls{IOT} is growing rapidly and it is changing the way people and machines interact with the world.
  33 While the term \gls{IOT} briefly gained interest around 1999 to describe the communication of \gls{RFID} devices \citep{ashton_internet_1999,ashton_that_2009}, it probably already popped up halfway the eighties in a speech by \citet{peter_t_lewis_speech_1985}:
  34
  35 \begin{quote}
  36         \emph{The \glsxtrlong{IOT}, or \glsxtrshort{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.}
  37 \end{quote}
  38
  39 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 \citep{evans_internet_2011}.
  40 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.
  41 These connected devices are already in households all around us in the form of smart electricity meters, fridges, phones, watches, home automation, \etc.
  42
  43 When describing \gls{IOT} systems, a tiered---or layered---architecture is often used to compartmentalize the technology.
  44 The number of tiers heavily depends on the required 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.
  45
  46 \begin{figure}[ht]
  47         \centering
  48         \includestandalone{iot-layers}
  49         \caption{A four-layer \gls{IOT} architecture.}%
  50         \label{fig:iot-layers}
  51 \end{figure}
  52
  53 Closest to the end-user is the presentation layer, it provides the interface between the user and the \gls{IOT} application.
  54 In home automation this may be a web interface or a app used on a phone or mounted tablet to interact with the edge devices and view the sensor data.
  55
  56 The application layer provides the \glspl{API}, interfaces and data storage.
  57 A cloud service or local server provides this layer in a typical home automation application.
  58
  59 All layers are connected using the network layer.
  60 In many applications this is implemented using conventional networking techniques such as WiFi or Ethernet.
  61 However, networks or layers on top of it tailored to the needs of \gls{IOT} applications have been increasingly popular such as \gls{BLE}, LoRa, ZigBee, LTE-M, or \gls{MQTT}.
  62
  63 The perception layer---also called edge layer---collects the data and interacts with the environment.
  64 It consists of edge devices such as microprocessors equipped with various sensors and actuators.
  65 In home automation this layer consists of all the devices hosting the sensors and actuators such as in a smart lightbulb, an actuator to open a door or a temperature and humidity sensor.
  66
  67 Across the layers, the devices are a large heterogeneous collection of different platforms, protocols, paradigms, and programming languages often resulting in impedance problems or semantic friction between layers when programming \citep{ireland_classification_2009}.
  68 Even more so, perception layer specifically often is a heterogeneous collections of microprocessors in itself as well, each having their own peculiarities, language of choice and hardware interfaces.
  69 As the edge hardware needs to be cheap, small-scale, and energy efficient, the microprocessors used to power these devices do not have a lot of computational power, only a soup\c{c}on of memory, and little communication bandwidth.
  70 Typically the devices do not run a full fledged \gls{OS} but a compiled firmware.
  71 This firmware is often written in an imperative language that needs to be flashed to the program memory.
  72 Program memory typically is flash based and only lasts a couple of thousand writes before it wears out.
  73 While devices are getting a bit faster, smaller, and cheaper, they keep these properties to an extent, greatly reducing the flexibility for dynamic systems where tasks are created on the fly, executed on demand, or require parallel execution.
  74 These problems can be mitigated by dynamically sending code to be interpreted to the microprocessor.
  75 With interpretation, a specialized interpreter is flashed in the program memory once that receives the program code to execute at runtime.
  76 Interpretation always comes with an overhead, making it challenging to create them for small edge devices.
  77 However, the hardware requirements can be reduced by embedding domain-specific data into the programming language to be interpreted, so called \glspl{DSL}.
  78
  79 \section{\texorpdfstring{\Glsxtrlongpl{DSL}}{Domain-specific languages}}\label{sec:back_dsl}
  80 % General
  81 Programming languages can be divided up into two categories: \glspl{DSL}\footnote{Historically this has been called DSEL as well.} and \glspl{GPL} \citep{fowler_domain_2010}.
  82 Where \glspl{GPL} are not made with a demarcated area in mind, \glspl{DSL} are tailor-made for a specific domain.
  83 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.
  84 \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).
  85
  86 \begin{figure}[ht]
  87         \centering
  88         \includestandalone{hyponymy_of_dsls}
  89         \caption{Hyponymy of \glspl{DSL} (adapted from \citet[\citepage{2}]{mernik_extensible_2013})}%
  90         \label{fig:hyponymy_of_dsls}
  91 \end{figure}
  92
  93 \subsection{Standalone and embedded}
  94 \glspl{DSL} where historically created as standalone languages, meaning all the machinery is developed solely for the language.
  95 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.
  96 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.
  97 Examples of standalone \glspl{DSL} are regular expressions, make, yacc, XML, SQL, \etc.
  98
  99 The dichotomous approach is embedding the \gls{DSL} in a host language, i.e.\ \glspl{EDSL} \citep{hudak_modular_1998}.
 100 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.
 101 There is more linguistic reuse~\cite{krishnamurthi_linguistic_2001}.
 102 There are however two sides to the this coin.
 103 If the syntax of the host language is not very flexible, the syntax of the \gls{DSL} may become clumsy.
 104 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}.
 105
 106 \subsection{Heterogeneity and homogeneity}
 107 \Citet{tratt_domain_2008} applied a notion from metaprogramming \citep{sheard_accomplishments_2001} to \glspl{EDSL} to define homogeneity and heterogeneity of \glspl{EDSL} as follows:
 108
 109 \begin{quote}
 110         \emph{
 111         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.
 112 }
 113 \end{quote}
 114
 115 Homogeneous \glspl{EDSL} are therefore languages that are solely defined as an extension to their host language.
 116 They often restrict features of the host language to provide a safer interface or capture an idiomatic pattern in the host language for reuse.
 117 The difference between a library and a homogeneous \glspl{EDSL} is not always clear.
 118 Examples of homogeneous \glspl{EDSL} are libraries such as ones for sets, \glspl{GUI} creation, LISP's macro system, \etc.
 119
 120 On the other hand, heterogeneous \glspl{EDSL} are languages that are not executed in the host language.
 121 For example, \citep{elliott_compiling_2003} 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.
 122 In fact, \gls{ITASK} and \gls{MTASK} are both heterogeneous \glspl{EDSL} and \gls{MTASK} specifically is a compiling \gls{DSL}.
 123
 124 \section{\texorpdfstring{\Glsxtrlong{TOP}}{Task-oriented programming}}\label{sec:back_top}
 125 \Gls{TOP} is a declarative programming paradigm designed to model interactive systems \citep{plasmeijer_task-oriented_2012}.
 126 Instead of dividing problems into layers or tiers, as is done in \gls{IOT} architectures, it deals with separation of concerns in a novel way.
 127 From the data types, utilising various \emph{type-parametrised} concepts, all other aspects are handled automatically (see \cref{fig:tosd}).
 128 This approach to software development is called \gls{TOSD} \citep{wang_maintaining_2018}.
 129
 130 \begin{figure}[ht]
 131         \centering
 132         \begin{subfigure}[t]{.5\textwidth}
 133                 \centering
 134                 \includestandalone{traditional}
 135                 \caption{Traditional layered approach.}
 136         \end{subfigure}%
 137         \begin{subfigure}[t]{.5\textwidth}
 138                 \centering
 139                 \includestandalone{tosd}
 140                 \caption{\Gls{TOSD} approach.}
 141         \end{subfigure}
 142         \caption{Separation of concerns in a traditional setting and in \gls{TOSD} (adapted from~\cite[\citepage{20}]{wang_maintaining_2018}).}%
 143         \label{fig:tosd}
 144 \end{figure}
 145
 146 \begin{description}
 147         \item[\Glsxtrshort{UI} (presentation layer):]
 148                 The \gls{UI} of the system is automatically generated from the representation of the type.
 149                 Even though the \gls{UI} is generated from the structure of the datatypes, in practical \gls{TOP} systems it can be tweaked afterwards to suit the specific needs of the application.
 150         \item[Tasks (business layer):]
 151                 A task is an abstract representation of a piece of work that needs to be done.
 152                 It provides an intuitive abstraction over work in the real world.
 153                 Just as with real-life tasks and workflow, tasks can be combined in various ways such as in parallel or in sequence.
 154                 Furthermore, a task is observable which means it is possible to observe a---partial---result during execution and act upon it by for example starting new tasks.
 155                 Examples of tasks are filling in a form, sending an email, reading a sensor or even doing a physical task.
 156         \item[\Glsxtrshortpl{SDS} (resource access):]
 157                 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.
 158                 Tasks can also share data using \glspl{SDS}, an abstraction over any data.
 159                 An \gls{SDS} can represent typed data stored in a file, a chunk of memory, a database \etc.
 160                 \Glspl{SDS} can also represent external impure data such as the time, random numbers or sensory data.
 161                 Similar to tasks, transformation and combination of \glspl{SDS} is possible.
 162         \item[Programming language (\glsxtrshort{UOD}):]
 163                 The \gls{UOD} from the business layer is explicitly and separately modelled by the relations that exist in the functions of the host language.
 164 \end{description}
 165
 166
 167 \subsection{\texorpdfstring{\Gls{ITASK}}{ITask}}
 168 The concept of \gls{TOP} originated from the \gls{ITASK} framework, a declarative workflow language for defining multi-user distributed web applications implemented as an \gls{EDSL} in the lazy pure \gls{FP} language \gls{CLEAN} \citep{plasmeijer_itasks:_2007,plasmeijer_task-oriented_2012}.
 169 From the structural properties of the data types, the entire user interface is automatically generated.
 170
 171 As an example, \cref{fig:enter_person} shows the \gls{ITASK} code and the corresponding \gls{UI} for a simple task for entering a person.
 172 From the data type definitions (\crefrange{lst:dt_fro}{lst:dt_to}), using generic programming (\cref{lst:dt_derive}), the \glspl{UI} for the data types are automatically generated.
 173 Using task combinators (see \cleaninline{>>!} at \cref{lst:task_comb}), the tasks can be combined in sequence.
 174 Only when the user entered a complete value in the web editor, then the continue button enables and the result can be viewed.
 175 Special combinators (e.g.\ \cleaninline{@>>} at \cref{lst:task_ui}) are available to tweak the \gls{UI} afterwards.
 176
 177 \begin{figure}[ht]
 178         \begin{subfigure}[b]{.525\linewidth}
 179                 \begin{lstClean}
 180 :: Person =[+\label{lst:dt_fro}+]
 181         { name        :: String
 182         , gender      :: Gender
 183         , dateOfBirth :: Date
 184         }
 185
 186 :: Gender
 187         = Male
 188         | Female
 189         | Other String[+\label{lst:dt_to}+]
 190
 191 derive class iTask Person, Gender[+\label{lst:dt_derive}+]
 192
 193 enterPerson :: Task Person
 194 enterPerson
 195         =   Hint "Enter a person:"
 196                 @>> enterInformation [] [+\label{lst:task_ui}+]
 197         >>! \result -> Hint "You Entered:"[+\label{lst:task_comb}+]
 198                 @>> viewInformation [] result
 199                 \end{lstClean}
 200                 \caption{\Gls{CLEAN} code}
 201         \end{subfigure}%
 202         \begin{subfigure}[b]{.475\linewidth}
 203                 \includegraphics[width=\linewidth]{person0}
 204                 \includegraphics[width=\linewidth]{person1}
 205                 \includegraphics[width=\linewidth]{person2}
 206                 \caption{\Glsxtrlong{UI}}
 207         \end{subfigure}
 208         \caption{The \gls{UI} and code for entering a person in \gls{ITASK}.}%
 209         \label{fig:enter_person}
 210 \end{figure}
 211
 212 \subsection{Other \texorpdfstring{\glsxtrshort{TOP}}{TOP} languages}
 213 \Citet{steenvoorden_tophat_2022} defines two instruments for \gls{TOP}: \gls{TOP} languages and \gls{TOP} engines.
 214 A \gls{TOP} language is a formal language to specify workflows.
 215 A \gls{TOP} engine executes such a specification as a ready-for-work application.
 216 The \gls{ITASK} system is both a \gls{TOP} language and an engine.
 217 While \gls{ITASK} conceived \gls{TOP}, it is not the only \gls{TOP} language.
 218 Some \gls{TOP} languages and systems arose from Master's and Bachelor's thesis projects (e.g.\ \textmu{}Task \citep{piers_task-oriented_2016} and LTasks \citep{van_gemert_task_2022}) or were created to solve a practical problem (e.g.\ Toppyt \citep{lijnse_toppyt_2022} and hTask \citep{lubbers_htask_2022}).
 219 Furthermore, \gls{TOPHAT} is a fully formally specified \gls{TOP} language designed to capture the essence of \gls{TOP} formally \citep{steenvoorden_tophat_2019}.
 220 It is also possible to translate \gls{TOPHAT} code to \gls{ITASK} to piggyback on the \gls{TOP} engine it offers.
 221
 222 \subsection{\texorpdfstring{\Gls{MTASK}}{MTask}}
 223 Finally there is \gls{MTASK}, a \gls{TOP} language designed for defining workflows for \gls{IOT} edge devices \citep{koopman_task-based_2018}.
 224 It is written in \gls{CLEAN} as a multi-view \gls{EDSL} fully integrated with \gls{ITASK}.
 225 Together with \gls{ITASK}, it allows the programmer to define all layers of an \gls{IOT} system from a single declarative specification.
 226 The domain-specific nature of the language allows for a very compact binary representation of the work that needs to be done.
 227 This specification can be interpreted on a device that runs the \gls{MTASK} \gls{RTS}, a domain-specific \gls{TOP} engine implemented as a feather-light domain-specific \gls{OS}.
 228
 229 \section{Reading guide and contributions}\label{sec:contributions}
 230 This novel view on programming \gls{IOT} systems is presented in the thesis as a purely functional rhapsody in three episodes.
 231 On Wikipedia, a rhapsody is defined as follows \citep{wikipedia_contributors_rhapsody_2022}:
 232 \begin{quote}
 233         \emph{A \emph{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.
 234         An air of spontaneous inspiration and a sense of improvisation make it freer in form than a set of variations.}
 235 \end{quote}
 236
 237 \subsection{\nameref{prt:dsl}}
 238 The \gls{MTASK} system is a heterogeneous \gls{EDSL} and during the development of it, several novel basal techniques for embedding \glspl{DSL} in \gls{FP} languages have been found.
 239 This first episode is a cumulative---otherwise known as paper-based---episode consisting of two papers published on novel embedding techniques.
 240 Both papers are readable independently.
 241
 242 \subsubsection*{\Fullref{chp:classy_deep_embedding}}
 243 This chapter is based on the paper: \citeentry{lubbers_deep_2022}\todo{change in-press when published}.
 244
 245 While supervising \citeauthor{amazonas_cabral_de_andrade_developing_2018}'s \citeyear{amazonas_cabral_de_andrade_developing_2018} Master's thesis, 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.
 246 Slowly the ideas organically grew to form the technique shown in the paper.
 247 The related work section is updated with the research found only after publication.
 248 \Cref{sec:classy_reprise} was added after publication and contains a (yet) unpublished extension of the embedding technique for reducing the required boilerplate.
 249 The research from this paper and writing the paper was solely performed by me.
 250
 251 \subsubsection*{\Fullref{chp:first-class_datatypes}}
 252 This chapter is based on the paper: \citeentry{lubbers_first-class_2022}\todo{change when accepted}.
 253
 254 It shows how to inherit data types from the host language in \glspl{EDSL} using metaprogramming.
 255 It does so by providing a proof-of-concept implementation using \gls{HASKELL}'s metaprogramming system: \glsxtrlong{TH}.
 256 Besides showing the result, the paper also serves as a gentle introduction to using \glsxtrlong{TH} and contains a thorough literature study on research that uses \glsxtrlong{TH}.
 257 The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman and Rinus Plasmeijer in which we discussed and refined the ideas.
 258
 259 \subsection{\nameref{prt:top}}
 260 This is a monograph compiled from several papers and revised lecture notes on \gls{MTASK}, the \gls{TOP} system used to orchestrate the \gls{IOT}.
 261 It provides a gentle introduction to the \gls{MTASK} system elaborates on \gls{TOP} for the \gls{IOT}.
 262 \todo[inline]{outline the chapters}
 263
 264 \begin{itemize}
 265         \item \citeentry{koopman_task-based_2018}
 266
 267                 This is the initial \gls{TOP}/\gls{MTASK} paper.
 268                 It provides an overview of the initial \gls{MTASK} language and shows first versions of a pretty printer, an \gls{ITASK} simulation and a \gls{C} code generation view.
 269                 \paragraph{Contribution}
 270                 Pieter Koopman wrote it, I helped with the software and research.
 271         \item \citeentry{lubbers_task_2018}
 272
 273                 This paper was an extension of my Master's thesis \citep{lubbers_task_2017}.
 274                 It shows how a simple imperative variant of \gls{MTASK} was integrated with \gls{ITASK}.
 275                 While the language was a lot different than later versions, the integration mechanism is still used in \gls{MTASK} today.
 276                 \paragraph{Contribution}
 277                 The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman and Rinus Plasmeijer in which we discussed and refined the ideas.
 278         \item \citeentry{lubbers_multitasking_2019}\footnote{%
 279                 This work acknowledges the support of the ERASMUS+ project ``Focusing Education on Composability, Comprehensibility and Correctness of Working Software'', no. 2017--1--SK01--KA203--035402
 280                 }
 281
 282                 This paper was a short paper on the multitasking capabilities of \gls{MTASK} in contrast to traditional multitasking methods for \gls{ARDUINO}.
 283                 \paragraph{Contribution}
 284                 The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman and Rinus Plasmeijer.
 285         \item \citeentry{koopman_simulation_2018}\footnotemark[\value{footnote}]\todo{change when published}
 286
 287                 These revised lecture notes are from a course on the \gls{MTASK} simulator was provided at the 2018 \gls{CEFP}/\gls{3COWS} winter school in Ko\v{s}ice, Slovakia.
 288                 \paragraph{Contribution}
 289                 Pieter Koopman wrote and taught it, I helped with the software and research.
 290         \item \citeentry{lubbers_writing_2019}\footnotemark[\value{footnote}]\todo{change when published}
 291
 292                 These revised lecture notes are from a course on programming in \gls{MTASK} provided at the 2019 \gls{CEFP}/\gls{3COWS} summer school in Budapest, Hungary.
 293                 \paragraph{Contribution}
 294                 Pieter Koopman prepared and taught half of the lecture and supervised the practical session.
 295                 I taught the other half of the lecture, wrote the lecture notes, made the assignments and supervised the practical session.
 296         \item \citeentry{lubbers_interpreting_2019}
 297
 298                 This paper shows an implementation for \gls{MTASK} for microcontrollers in the form of a compilation scheme and informal semantics description.
 299                 \paragraph{Contribution}
 300                 The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman and Rinus Plasmeijer.
 301         \item \citeentry{crooijmans_reducing_2022}\todo{change when published}
 302
 303                 This paper shows how to create a scheduler so that devices running \gls{MTASK} tasks can go to sleep more automatically.
 304                 \paragraph{Contribution}
 305                 The research was carried out by \citet{crooijmans_reducing_2021} during his Master's thesis.
 306                 I did the daily supervision and helped with the research, Pieter Koopman was the formal supervisor and wrote most of the paper.
 307         \item \emph{Green Computing for the Internet of Things}\footnote{
 308                 This work acknowledges the support of the Erasmus+ project ``SusTrainable---Promoting Sustainability as a Fundamental Driver in Software Development Training and Education'', no. 2020--1--PT01--KA203--078646}\todo{change when published}
 309
 310                 \paragraph{Contribution}
 311                 These revised lecture notes are from a course on sustainable programming using \gls{MTASK} provided at the 2022 SusTrainable summer school in Rijeka, Croatia.
 312                 Pieter prepared and taught a quarter of the lecture and supervised the practical session.
 313                 I prepared and taught the other three quarters of the lecture, made the assignments and supervised the practical session\todo{writing contribution}.
 314 \end{itemize}
 315
 316 \subsection{\nameref{prt:tvt}}
 317 \Cref{prt:tvt} is based on a journal paper that quantitatively and qualitatively compares traditional \gls{IOT} architectures with \gls{IOT} systems using \gls{TOP} and contains a single chapter.
 318 This chapter is based on the journal paper: \citeentry{lubbers_could_2022}\todo{change when published}\footnote{This work is an extension of the conference article: \citeentry{lubbers_tiered_2020}\footnotemark{}}.
 319 \footnotetext{This paper was partly funded by the Radboud-Glasgow Collaboration Fund.}
 320
 321 It compares programming traditional tiered architectures to tierless architectures by showing a qualitative and a quantitative four-way comparison of a smart-campus application.
 322
 323 \paragraph{Contribution}
 324 Writing the paper was performed by all authors.
 325 I created the server application, the \gls{CLEAN}/\gls{ITASK}/\gls{MTASK} implementation (\glsxtrshort{CWS}) and the \gls{CLEAN}/\gls{ITASK} implementation (\glsxtrshort{CRS})
 326 Adrian Ramsingh created the \gls{MICROPYTHON} implementation (\glsxtrshort{PWS}), the original \gls{PYTHON} implementation (\glsxtrshort{PRS}) and the server application were created by \citet{hentschel_supersensors:_2016}.
 327
 328 \input{subfilepostamble}
 329 \end{document}