\chapter{Prelude}%
\label{chp:introduction}
\begin{chapterabstract}
- This chapter introduces the dissertation and thesis by providing:
+ This chapter introduces the dissertation by providing:
\begin{itemize}
- \item a general introduction to the topics and research venues;
+ \item a general introduction to the topics and research directions;
\item a reading guide;
\item background material on the \glsxtrlong{IOT}, \glsxtrlongpl{DSL}, \glsxtrlong{TOP}, \gls{ITASK}, and \gls{MTASK};
\item and a detailed overview of the scientific contributions.
\end{itemize}
\end{chapterabstract}
-There are at least 13.4 billion devices connected to the internet at the time of writing\footnote{\url{https://transformainsights.com/research/tam/market}, accessed on: \formatdate{13}{10}{2022}}.
-Each of these senses, acts, or otherwise interacts with people, other computers, and the environment surrounding us.
-Despite their immense diversity, they are all computers.
-And as computers, they require software to operate.
+There are at least 13.4 billion devices connected to the internet at the time of writing \citep{transforma_insights_current_2023}.
+Each of these sense, act, or otherwise, interacts with people, computers, and the environment.
+Despite their immense diversity in characteristics, they are all computers and they they all require software to operate.
-An increasing amount of these connected devices are so-called \emph{edge devices} that operate in the \gls{IOT}.
-Edge devices are the leafs of the \gls{IOT} systems, they perform the interaction with the physical world.
+An increasing number of these connected devices are so-called \emph{edge devices} that operate in the \gls{IOT}.
+Edge devices are the leaves of the \gls{IOT} systems.
+They perform the interaction with the physical world and are often physically embedded in the fabric itself, residing usually in hard-to-reach places such as light bulbs, clothing, smart electricity meters, buildings, or even farm animals.
Typically, these edge devices are powered by microcontrollers.
-These miniature computers contain integrated circuits that accomodates a microprocessor designed for use in embedded applications.
-Typically, microcontrollers are therefore tiny; have little memory; contain a slow, but energy-efficient processor; and allow for a lot of connectivity for integrating peripherals such as sensors and actuators in order to interact with their surroundings.
-
-Unlike the conductor in the orchestra waving their baton to instruct the ensemble of instruments, in the universe of software there is room for little error.
-In the traditional setting, an \gls{IOT} engineer has to program each device and their interoperation using different programming paradigms, programming languages, and abstraction levels.
-Thus resulting in semantic friction, making programming and maintaining \gls{IOT} systems is a complex and error-prone process.
-
-This thesis describes the research carried out around orchestrating these complex \gls{IOT} systems using \gls{TOP}.
+Microcontrollers are equipped with a lot of connectivity for integrating peripherals such as sensors and actuators.
+The connectivity makes them very suitable to interact with their surroundings.
+These miniature computers contain integrated circuits that accommodate a microprocessor designed for use in embedded applications.
+As a consequence, microcontrollers are cheap; tiny; have little memory; and contain a slow, but energy-efficient processor.
+
+Unlike the conductor in an orchestra waving their baton to instruct the ensemble of instruments, in the universe of software there is room for little error.
+Moreover, in dynamic \gls{IOT} applications, there is not always a coordinating conductor.
+Edge devices---the instruments---come and go, perform their own pieces, or are sometimes instructed to perform a certain piece, they might even operate without a central authority.
+In a traditional setting, an \gls{IOT} engineer has to program each device and their interoperation using different programming paradigms, programming languages, and abstraction levels.
+This results in semantic friction, which makes programming and maintaining \gls{IOT} systems a complex and error-prone process.
+
+This dissertation describes the research carried out around orchestrating these complex \gls{IOT} systems using \gls{TOP}.
\Gls{TOP} is an innovative tierless programming paradigm for interactive multi-layered systems.
-By utilising advanced compiler technologies, much of the internals, communications, and interoperations between the tiers\slash{}layers of the applications is automatically generated.
+By utilising advanced compiler technologies, much of the internals, communication, and interoperation between the tiers or layers of the applications are automatically generated.
From a single declarative specification of the work required, the compiler makes a ready-for-work application consisting of interconnected components for all tiers.
-For example, the \gls{TOP} system \gls{ITASK} can be used to program all layers of a multi-user distributed web applications from a single source specification.
-It is implemented in \gls{CLEAN} and executes also in \gls{CLEAN}'s run time.
-The final executable is very low level and contains all these abstraction levels, this results in increased hardware requirements.
-The high hardware requirements are no problem for regular computers but impractical for the average edge device.
+For example, the \gls{TOP} system \gls{ITASK} is used to program all layers of multi-user distributed web applications from a single source specification.
+It is implemented in the general-purpose lazy functional programming language \gls{CLEAN}, and therefore requires relatively powerful hardware.
+The inflated hardware requirements are no problem for regular computers but impractical for the average edge device.
This is where \glspl{DSL} must be brought into play.
\Glspl{DSL} are programming languages created with a specific domain in mind.
-Consequently, jargon does not have to be expressed in the language itself, but they can be built-in features.
-As a result, hardware requirements can be drastically lowered, even with high levels of abstraction for the specified domain.
+Consequently, jargon does not have to be expressed in terms of the language itself, but they can be built-in features.
+Furthermore, the \gls{DSL} can eschew language or system features that are irrelevant for the domain.
+Using \glspl{DSL}, hardware requirements can be drastically lowered, even while maintaining a high abstraction level for the specified domain.
-To incorporate the plethora of edge devices in the orchestra of an \gls{IOT} system, the \gls{MTASK} system is used.
-\Gls{MTASK} is a novel programming language for programming \gls{IOT} edge devices using \gls{TOP}.
-Where \gls{ITASK} abstracts away from the gritty details of multi-tier web applications, \gls{MTASK} has domain-specific abstractions for \gls{IOT} edge devices, maintaining the high abstraction level that \gls{TOP} generally offers.
+To incorporate the plethora of edge devices in the orchestra of a \gls{TOP} system, the \gls{MTASK} system is used.
+The \gls{MTASK} language is a novel programming language for programming \gls{IOT} edge devices using \gls{TOP}.
+Where \gls{ITASK} abstracts away from the gritty details of multi-tier web applications, \gls{MTASK} has domain-specific abstractions for \gls{IOT} edge devices, maintaining the high abstraction level that \gls{TOP} offers.
As it is integrated with \gls{ITASK}, it allows for all layers of an \gls{IOT} application to be programmed from a single source.
\section{Reading guide}%
\label{lst:reading_guide}
This work is structured as a purely functional rhapsody.
-On Wikipedia, a musical rhapsody is defined as follows \citep{wikipedia_contributors_rhapsody_2022}:
+The \citet{wikipedia_contributors_rhapsody_2022} define a musical rhapsody is defined as follows:
\begin{quote}\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.}
\end{quote}
-%The three episodes in this thesis are barded by the introduction and conclusion (\cref{chp:introduction,chp:conclusion}).
+This dissertation consists of three episodes.
\Cref{prt:dsl} is a paper-based---otherwise known as cumulative---episode containing chapters that provide insight in advanced \gls{DSL} embedding techniques for \gls{FP} languages.
-The chapters are readable independently.
+The chapters can be read independently from each other.
\Cref{prt:top} is a monograph showing \gls{MTASK}, a \gls{TOP} \gls{DSL} for the \gls{IOT}.
-Hence, the chapters are best read in order.
-It introduces \gls{IOT} edge device programming, shows the complete \gls{MTASK} language, provides details on how \gls{MTASK} is integrated with \gls{ITASK}, shows how the byte code compiler is implemented, with a guide for green computing with \gls{ITASK} and ends with a conclusion and overview of future and related work.
+Hence, the chapters in this episode are best read in order.
+It introduces \gls{IOT} edge device programming, shows the complete \gls{MTASK} language, provides details on how \gls{MTASK} is integrated with \gls{ITASK}, shows how the byte code compiler is implemented, presents a guide for green computing with \gls{MTASK}, and ends with a conclusion and overview of future and related work.
\Cref{prt:tvt} is a single chapter based on a journal article in which traditional tiered \gls{IOT} programming is qualitatively and quantitatively compared to tierless programming using a real-world application.
The chapter is readable independently.
\end{quote}
Much later, CISCO states that the \gls{IOT} started when there were as many connected devices as there were people on the globe, i.e.\ around 2008 \citep{evans_internet_2011}.
-Today, \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 they live in.
+Today, \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 they operate in.
These connected devices are already in households all around us in the form of smart electricity meters, fridges, phones, watches, home automation, \etc.
When describing \gls{IOT} systems, a tiered---or layered---architecture is often used for compartmentalisation.
-The number of tiers heavily depends on the required complexity of the model.
+The number of tiers depends on the required complexity of the model.
For the intents and purposes of this thesis, the layered architecture as shown in \cref{fig:iot-layers} is used.
\begin{figure}
\label{fig:iot-layers}
\end{figure}
-To explain the tiers, an example \gls{IOT} application---home automation---is dissected accordingly.
-Closest to the end-user is the presentation layer, it provides the interface between the user and \gls{IOT} systems.
-In home automation this may be a web interface, or an app used on a phone or wall-mounted tablet to interact with edge devices and view sensor data.
+To explain the tiers, an example \gls{IOT} application---home automation---is dissected.
+Closest to the end-user is the presentation layer, it provides the interface between the user and the \gls{IOT} system.
+In home automation this may be a web interface, an app used on a phone, or wall-mounted tablet to interact with edge devices and view sensor data.
-The application layer provides the \glspl{API}, data interfaces, data processing, and data storage of \gls{IOT} systems.
+The application layer provides the \glspl{API}, data interfaces, data storage processing, and data processing of \gls{IOT} systems.
A cloud server or local server provides this layer in a typical home automation application.
The perception layer---also called edge layer---collects the data and interacts with the environment.
It consists of edge devices such as microcontrollers equipped with various sensors and actuators.
-In home automation this layer consists of all the devices hosting sensors and actuators such as smart light bulbs, actuators to open doors, or temperature and humidity sensors.
+In home automation this layer consists of all devices hosting sensors and actuators such as smart light bulbs, actuators to open doors, or temperature and humidity sensors.
All layers are connected using the network layer.
In some applications this is implemented using conventional networking techniques such as Wi-Fi or Ethernet.
-However, network technology that is tailored to the needs of the specific interconnection between the two layers have become increasingly popular.
+However, network technology that is tailored to the needs of the specific interconnection between two layers is increasingly popular.
Examples of this are BLE, LoRa, ZigBee, and LTE-M as a communication protocol for connecting the perception layer to the application layer using \gls{IOT} transport protocols such as \gls{MQTT}.
-Protocols such as HTTP, AJAX, and WebSocket connecting the presentation layer to the application layer that are designed for the use in web applications.
+Protocols such as HTTP, AJAX, and WebSocket connecting the presentation layer to the application layer that are designed for the use in web applications.
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}.
-Even more so, the perception layer itself is often a heterogeneous collection of microcontrollers in itself, each having their own peculiarities, language of choice, and hardware interfaces.
-As edge hardware needs to be cheap, small-scale, and energy efficient, the microcontrollers used to power them do not have a lot of computational power, only a soup\c{c}on of memory, and little communication bandwidth.
+Even more so, the perception layer itself is often a heterogeneous collection of microcontrollers in itself, each having their own peculiarities, programming language of choice, and hardware interfaces.
+As edge hardware needs to be cheap, small scale, and energy efficient, the microcontrollers used to power them do not have a lot of computational power, only a smidge of memory, and little communication bandwidth.
Typically, these devices are unable to run a full-fledged general-purpose \gls{OS}.
Rather they employ compiled firmware written in imperative languages that combines all tasks on the device in a single program.
-While devices are getting a bit faster, smaller, and cheaper, they keep these properties to an extent, greatly reducing the flexibility for dynamic systems when tasks are created on the fly, executed on demand, or require parallel execution.
-As program memory is mostly flash-based and only lasts a couple of thousands of writes before it wears out, it is not suitable for rapid reconfiguring and reprogramming.
+While devices are getting a bit faster, smaller, and cheaper, they keep these properties to an extent.
+For example, more powerful microcontrollers are capable of running \glspl{RTOS}, but this still requires a lot of resources and fixes the programs at compile time.
+As a consequence, the flexibility is greatly reduced for dynamic systems in which tasks are created on the fly, executed on demand, require parallel execution, or have dynamic scheduling behaviour.
+As program memory is mostly flash-based and only lasts a couple of thousands of writes before it wears out, it is not suitable for repeated reconfiguring and reprogramming.
These problems can be mitigated by dynamically sending code to be interpreted to the microcontroller.
With interpretation, a specialized interpreter is flashed in the program memory once it receives the program code to execute at run time.
Therefore, as the programs are not stored in the flash memory, it does not wear out.
It is challenging to create interpreters for small edge devices due to the severe hardware restrictions.
-However, the hardware requirements can be reduced by embedding domain-specific data into the langauge, so called \gls{DSL}; and the interpreter, a domain-specific \gls{OS}.
+This dissertation describes a \gls{DSL} that includes the high-level programming concepts of \gls{TOP}, while it can be executed on edge devices with very limited hardware requirements.
+It does so by compiling the \gls{DSL} to byte code that is executed in a feather-light domain-specific \gls{OS}.
\section{\texorpdfstring{\Glsxtrlongpl{DSL}}{Domain-specific languages}}%
\label{sec:back_dsl}
% General
-Programming languages can be divided up into two categories: \glspl{DSL}\footnotemark\ and \glspl{GPL} \citep{fowler_domain_2010}.
-\footnotetext{Historically \glsxtrshortpl{DSL} have been called DSELs as well.}
+Programming languages can be divided up into two categories: \glspl{DSL} and \glspl{GPL} \citep{fowler_domain_2010}.
Where \glspl{GPL} are not made with a demarcated area in mind, \glspl{DSL} are tailor-made for a specific domain.
-Writing idiomatic domain-specific code in a \gls{DSL} is easier and requires less background knowledge about a \gls{GPL}.
+Writing idiomatic domain-specific code in a \gls{DSL} is easier and requires less \gls{GPL} knowledge for a domain expert.
This does come at the cost of the \gls{DSL} being sometimes less expressive to an extent that it may not even be Turing complete.
\Glspl{DSL} come in two main flavours: standalone and embedded (\cref{sec:standalone_embedded})\footnote{Standalone and embedded are also called external and internal respectively.}.
Standalone languages are languages for which the complete toolchain has been developed, just as for any other \gls{GPL}.
-Embedded languages piggyback on an existing \gls{GPL}, they are defined in terms of their host language.
+Embedded languages piggyback on an existing language, they are defined in terms of their host language.
\Glspl{EDSL} can further be classified into heterogeneous and homogeneous languages (\cref{sec:hetero_homo}).
-In homogeneous languages all components are integrated whereas in heterogeneous \glspl{DSL}, some parts are ignorant of the other systems, e.g.\ a \gls{DSL} that generates code that is compiled by an existing compiler.
+In homogeneous languages all components are integrated whereas in heterogeneous \glspl{DSL}, some parts are agnostic of the other systems, e.g.\ a \gls{DSL} that generates code for execution on a totally different system.
This hyponymy is shown in \cref{fig:hyponymy_of_dsls}.
\begin{figure}
\centering
\includestandalone{hyponymy_of_dsls}
- \caption{A hyponymy of \glspl{DSL} (adapted from \citet[\citepage{2}]{mernik_extensible_2013})}%
+ \caption{A hyponymy of \glspl{DSL} (adapted from \citet[\citepage{2}]{mernik_extensible_2013}).}%
\label{fig:hyponymy_of_dsls}
\end{figure}
\subsection{Standalone and embedded}%
\label{sec:standalone_embedded}
-\glspl{DSL} where historically created as standalone languages, meaning that all machinery is developed solely for the language.
+\glspl{DSL} were historically created as standalone languages, meaning that all machinery is developed solely for the language.
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.
Unfortunately it also means that they need to develop a compiler or interpreter, and all the scaffolding for the language, making standalone \glspl{DSL} costly to create.
-Examples of standalone \glspl{DSL} are regular expressions, make, yacc, XML, SQL, \etc.
+Examples of standalone \glspl{DSL} are \TeX, make, yacc, XML, SQL, \etc.
-The dichotomous approach is embedding the \gls{DSL} in a host language, i.e.\ \glspl{EDSL} \citep{hudak_modular_1998}.
+The dichotomous approach to standalone \glspl{DSL} is embedding the \gls{DSL} in a host language, i.e.\ \glspl{EDSL} \citep{hudak_modular_1998}.
By defining the language as constructs in the host language, much of the machinery is inherited \citep{krishnamurthi_linguistic_2001}.
-This greatly reduces the cost of creating embedded languages.
+This greatly reduces the cost of creating embedded languages and shields the user from having to learn the host language and toolchain.
However, there are two sides to this coin.
-If the syntax of the host language is not very flexible, the syntax of the \gls{DSL} may become clumsy.
+If the syntax of the host language is not very flexible, the syntax of the \gls{DSL} can become clumsy.
Furthermore, \gls{DSL} 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}.
\Gls{FP} languages are especially suitable for hosting embedded \glspl{DSL}.
-They offer tooling for building abstraction levels by a strong and versatile type systems, minimal but flexible syntax, and offer referential transparency.
+They offer tooling for building abstraction levels by a strong and versatile type system, minimal but flexible syntax, and referential transparency.
\subsection{Heterogeneity and homogeneity}%
\label{sec:hetero_homo}
-\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:
+\Citet{tratt_domain_2008} applies a notion from metaprogramming \citep{sheard_accomplishments_2001} to \glspl{EDSL} to define homogeneity and heterogeneity of \glspl{EDSL} as follows:
\begin{quote}
\emph{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.
}
\end{quote}
-Homogeneous \glspl{EDSL} are therefore languages that are solely defined as an extension to their host language.
+Homogeneous \glspl{EDSL} are languages that are solely defined as an extension to their host language.
They often restrict features of the host language to provide a safer interface or capture an idiomatic pattern in the host language for reuse.
The difference between a library and a homogeneous \glspl{EDSL} is not always clear.
Examples of homogeneous \glspl{EDSL} are libraries such as ones for sets, regions, but also more complex tasks such as \glspl{GUI}.
On the other hand, heterogeneous \glspl{EDSL} are languages that are not executed in the host language.
For example, \citet{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.
-In fact, \gls{ITASK} and \gls{MTASK} are embedded \glspl{DSL}.
-\Gls{ITASK} runs in its host language as well, so it is a homogeneous \gls{DSL}.
-Tasks written using \gls{MTASK} are dynamically compiled to byte code for an edge device and is therefore a heterogeneous \gls{DSL}.
+
+Both \gls{ITASK} and \gls{MTASK} are \glspl{EDSL}.
+Programs written in \gls{ITASK} run in the host language, and it is a homogeneous \gls{DSL}.
+Tasks written using \gls{MTASK} are dynamically compiled to byte code for an edge device, making it a heterogeneous \gls{DSL}.
+The interpreter running on the edge device has no knowledge of the higher level task specification.
+It just interprets the byte code it was sent and takes care of the communication.
\section{\texorpdfstring{\Glsxtrlong{TOP}}{Task-oriented programming}}%
\label{sec:back_top}
-\Gls{TOP} is a recent declarative programming paradigm for modelling interactive systems \citep{plasmeijer_task-oriented_2012}.
-In \gls{TOP} languages, tasks are the basic building blocks.
-They represent the actual work.
-Instead of dividing problems into layers \gls{TOP} deals with separation of concerns in a novel way.
-From the data types, utilising various \emph{type-parametrised} concepts, all other aspects are handled automatically (see \cref{fig:tosd}).
+\Gls{TOP} is a declarative programming paradigm for modelling interactive systems \citep{plasmeijer_task-oriented_2012}.
+Instead of dividing problems into layers, \gls{TOP} deals with separation of concerns in a novel way.
This approach to software development is called \gls{TOSD} \citep{wang_maintaining_2018}.
\begin{figure}
\end{figure}
\begin{description}
- \item[\Gls{UI}:]
- The \gls{UI} of the system is automatically generated from the structural representation of the type.
- Though, practical \gls{TOP} systems allow tweaking afterwards to suit the specific needs of the application.
+ \item[Types:]
+ As can be seen from \cref{fig:tosd}, types are the pivotal component in \gls{TOP}.
+ From the data types, utilising various \emph{type-parametrised} concepts, all other aspects are handled automatically.
+ Hence, all other components arise from and depend on the types in the program.
\item[Tasks:]
+ In \gls{TOP} languages, tasks are the basic building blocks.
A task is an abstract representation of a piece of work that needs to be done.
- It provides an intuitive abstraction over work in the real world.
- Tasks are observable during execution.
- It is possible to observe a---partial---result and act upon it, e.g.\ by starting new tasks.
+ It provides an abstraction over work in the real world.
+ The nature of tasks makes them observable during execution.
+ It is possible to observe the current task value act upon it, e.g.\ taking a partial result as good enough, or by starting new tasks.
Examples of tasks are filling forms, sending emails, reading sensors or even doing physical tasks.
Just as with real-life tasks, multiple tasks can be combined in various ways such as in parallel or in sequence to form workflows.
Such combination operators are called task combinators.
\item[\Glspl{SDS}:]
Tasks mainly communicate using their observable task values.
- However, some collaboration requires tasks that are not necessarily related to share data.
+ However, some collaboration patterns are more easily expressed by tasks that share common data.
\Glspl{SDS} fill this gap, they offer a safe abstraction over any data.
- An \gls{SDS} can represent typed data stored in a file, a chunk of memory, a database \etc.
+ An \gls{SDS} can represent typed data stored in a file, a chunk of memory, a database, \etc.
\Glspl{SDS} can also represent external impure data such as the time, random numbers or sensor data.
- In many \gls{TOP} langauges, combinators are available to filter, combine, transform, and focus \glspl{SDS}.
+ In many \gls{TOP} languages, combinators are available to filter, combine, transform, and focus \glspl{SDS}.
+ \item[\Gls{UI}:]
+ The \gls{UI} of the system is automatically generated from the structural representation of the types.
+ Though, practical \gls{TOP} systems allow tweaking afterwards to suit the specific needs of the application.
\item[\Gls{UOD}:]
- The \gls{UOD} is explicitly and separately modelled by the relations that exist in the functions of the host language.
+ The \gls{UOD} is explicitly and separately modelled by the data types and relations that exist in the functions of the host language.
\end{description}
-\Cref{fig:tosd} differs from the presented \gls{IOT} architecture because they represent separate concepts.
-The \gls{IOT} architecture from \cref{fig:iot-layers} describes an execution architecture wheras the \gls{TOSD} figure describes a softwared development model.
-E.g.\ from a software development perspective, a task is a task, whether it is executed on a microcontroller, a server or a client.
-Only once a task is executed, the location of the execution becomes important, but this is taken care of by the system.
-Some concepts from the \gls{TOSD} model can be mapped upon the \gls{IOT} architecture though.
-Applying the concepts of \gls{TOSD} to \gls{IOT} systems can be done in two ways.
+\Cref{fig:tosd} differs from the presented \gls{IOT} architecture shown in \cref{fig:iot-layers} because they represent different concepts.
+The \gls{IOT} architecture is an execution architecture whereas \gls{TOSD} is a software development model.
+E.g.\ from a software development perspective, a task is a task, whether it is executed on a microcontroller, a server, or a client.
+Only when a task is executed, the location of the execution becomes important, but this is taken care of by the system.
+Some concepts from the \gls{TOSD} model can be mapped upon the \gls{IOT} architecture in two ways.
Firstly, edge devices can be seen as simple resources, thus accessed through \glspl{SDS}.
The second view is that edge devices contain miniature \gls{TOP} systems in itself.
The individual components in the miniature systems, the tasks, the \glspl{SDS}, are, in the eventual execution, connected to the main system.
-\todo{ik ben niet echt te\-vre\-den met deze \P}
-\subsection{\texorpdfstring{\Gls{ITASK}}{ITask}}
+\subsection{The \texorpdfstring{\gls{ITASK}}{iTask} system}
The concept of \gls{TOP} originated from the \gls{ITASK} framework, a declarative language and \gls{TOP} engine for defining interactive multi-user distributed web applications.
-\Gls{ITASK} is implemented as an \gls{EDSL} in the lazy pure \gls{FP} language \gls{CLEAN} \citep{plasmeijer_itasks:_2007,plasmeijer_task-oriented_2012}.
-From the structural properties of the data types, the entire user interface is automatically generated.
+The \gls{ITASK} system is implemented as an \gls{EDSL} in the programming language \gls{CLEAN}\footnote{\Cref{chp:clean_for_haskell_programmers} contains a guide for \gls{CLEAN} tailored to \gls{HASKELL} programmers.} \citep{plasmeijer_itasks:_2007,plasmeijer_task-oriented_2012}.
+From the structural properties of the data types and the current status of the work to be done, the entire \gls{UI} is automatically generated.
Browsers are powering \gls{ITASK}'s presentation layer.
The framework is built on top of standard web techniques such as JavaScript, HTML, and {CSS}.
-\Gls{ITASK} code running in the browser relies on an interpreter that operates on \gls{CLEAN}'s intermediate language \gls{ABC} \citep{staps_lazy_2019}.
+The browser runs the actual \gls{ITASK} code using an interpreter that operates on \gls{CLEAN}'s intermediate language \gls{ABC} \citep{staps_lazy_2019}.
+
Tasks in \gls{ITASK} have either \emph{no value}, an \emph{unstable} or a \emph{stable} task value.
For example, an editor for filling in a form initially has no value.
Once the user entered a complete value, its value becomes an unstable value, it can still be changed or even reverted to no value by emptying the editor again.
-Only when for example a continue button is pressed, a task becomes stable, fixing its value.
+Only when for example a continue button is pressed, a task value becomes stable, fixing its value.
The allowed task value transitions are shown in \cref{fig:taskvalue}.
-\begin{figure}[ht]
+\begin{figure}
\centering
\includestandalone{taskvalue}
\caption{Transition diagram for task values in \gls{ITASK}.}%
\end{figure}
As an example, \cref{lst:todo,fig:todo} show the code and \gls{UI} for an interactive to-do list application.
-The user can modify a shared to-do list through an editor directly or using some predefined actions.
+The user modifies a shared to-do list through an editor directly or using some predefined actions.
Furthermore, in parallel, the length of the list is shown to demonstrate \glspl{SDS}.
+Using \gls{ITASK}, complex collaborations of users and tasks can be described on a high level.
+
From the data type definitions (\cref{lst:todo_dt}), using generic programming (\cref{lst:todo_derive}), the \glspl{UI} for the data types are automatically generated.
-Then, using the parallel task combinator (\cleaninline{-\|\|}) that uses the left-hand side's result the task for updating the to-dos (\cref{lst:todo_update}) and the task for viewing the length are combined (\cref{lst:todo_length}).
+Then, using the parallel task combinator (\cleaninline{-\|\|}) the task for updating the to-dos (\cref{lst:todo_update}) and the task for viewing the length are combined (\cref{lst:todo_length}).
+This particular parallel combinator uses the result of the left-hand side task.
Both tasks operate on the to-do \gls{SDS} (\cref{lst:todo_sds}).
-The task for updating the to-do list is just an editor (\cref{lst:todo_editor}) combined using a step combinator (\crefrange{lst:todo_contfro}{lst:todo_contto}).
-The actions either change the value, sorting or clearing it, or terminates the task by returning the current value of the \gls{SDS}.
+The task for updating the to-do list is an editor (\cref{lst:todo_editor}) combined using a step combinator (\crefrange{lst:todo_contfro}{lst:todo_contto}).
+The actions either change the value, sorting or clearing it, or terminate the task by returning the current value of the \gls{SDS}.
Special combinators (e.g.\ \cleaninline{@>>} at \cref{lst:todo_ui}) are used to tweak the \gls{UI} to display informative labels.
+\cleaninputlisting[float=,firstline=6,lastline=22,tabsize=3,numbers=left,caption={The code for a shared to-do list in \gls{ITASK}.},label={lst:todo}]{lst/sharedlist.icl}
+
\begin{figure}
\centering
- \includegraphics[width=.75\linewidth]{todo0g}
+ \includegraphics[width=\linewidth]{todo0g}
\caption{The \gls{UI} for the shared to-do list in \gls{ITASK}.}%
\label{fig:todo}
\end{figure}
-\cleaninputlisting[float=,firstline=6,lastline=22,tabsize=3,numbers=left,caption={The code for the shared to-do list in \gls{ITASK}\footnotemark.},label={lst:todo}]{lst/sharedlist.icl}
-\footnotetext{\Cref{chp:clean_for_haskell_programmers} contains a guide for \gls{CLEAN} tailored to \gls{HASKELL} programmers.}
-
-\subsection{\texorpdfstring{\Gls{MTASK}}{MTask}}
-\Gls{ITASK} seems an obvious candidate at first glance for extending \gls{TOP} to \gls{IOT} edge devices.
-However, \gls{IOT} edge devices are in general not powerful enough to run or interpret \gls{CLEAN}\slash\gls{ABC} code, they just lack the processor speed and the memory.
-To bridge this gap, \gls{MTASK} was developed, a \gls{TOP} system for \gls{IOT} edge devices that is integrated in \gls{ITASK} \citep{koopman_task-based_2018}.
-\Gls{ITASK} abstracts away from details such as user interfaces, data storage, client-side platforms, and persistent workflows.
+\subsection{The \texorpdfstring{\gls{MTASK}}{mTask} system}
+The work for \gls{IOT} edge devices can often be succinctly described by \gls{TOP} programs.
+Software on microcontrollers is usually composed of smaller basic tasks, are interactive, and share data with other components or the server.
+The \gls{ITASK} system seems an obvious candidate for bringing \gls{TOP} to \gls{IOT} edge devices.
+However, an \gls{ITASK} application contains many features that are not needed on \emph{edge devices} such as higher-order tasks, support for a distributed architecture, or a multi-user web server.
+Furthermore, \gls{IOT} edge devices are in general not powerful enough to run or interpret \gls{CLEAN}\slash\gls{ABC} code, they just lack the processor speed and memory.
+To bridge this gap, \gls{MTASK} is developed, a domain-specific \gls{TOP} system for \gls{IOT} edge devices that is integrated in \gls{ITASK} \citep{koopman_task-based_2018}.
+The \gls{ITASK} language abstracts away from details such as user interfaces, data storage, client-side platforms, and persistent workflows.
On the other hand, \gls{MTASK} offers abstractions for edge layer-specific details such as the heterogeneity of architectures, platforms, and frameworks; peripheral access; (multi) task scheduling; and lowering energy consumption.
+
+The \gls{MTASK} system is seamlessly integrated with \gls{ITASK}.
+Tasks in \gls{MTASK} are integrated in such a way that they function as regular \gls{ITASK} tasks.
+Furthermore, \glspl{SDS} on the device can proxy \gls{ITASK} \glspl{SDS}.
+Using \gls{MTASK}, the programmer can define all layers of an \gls{IOT} system as a single declarative specification.
The \gls{MTASK} language is written in \gls{CLEAN} as a multi-view \gls{EDSL} and hence there are multiple interpretations possible.
The byte code compiler is the most relevant for this thesis.
From an \gls{MTASK} task constructed at run time, a compact binary representation of the work that needs to be done is compiled.
This byte code is then sent to a device that running the \gls{MTASK} \gls{RTS}.
-This feather-light domain-specific \gls{OS} is written in portable \gls{C} with a minimal device specific interface and functions as a \gls{TOP} engine.
-\Gls{MTASK} is seamlessly integrated with \gls{ITASK}: \gls{MTASK} tasks are integrated in such a way that they function as \gls{ITASK} tasks, and \glspl{SDS} on the device can tether an \gls{ITASK} \gls{SDS}.
-Using \gls{MTASK}, the programmer can define all layers of an \gls{IOT} system as a single declarative specification.
+This feather-light domain-specific \gls{OS} is written in portable \gls{C} with a minimal device specific interface and it executes the tasks using interpretation and rewriting.
-\Cref{lst:intro_blink,fig:intro_blink} shows the \gls{ITASK} part of the code and a screenshot of an interactive \imtask{} application for blinking \pgls{LED} on the microcontroller every dynamically changeable interval.
-Using \cleaninline{enterInformation}, the connection specification of the \gls{TCP} device is queried (\cref{lst:intro_enterDevice}).
-\Cref{lst:intro_withshared} defines \pgls{SDS} to communicate the blinking interval.
-Then the \gls{MTASK} is connected using \cleaninline{withDevice} at \cref{lst:intro_withdevice}.
-Once connected, the \cleaninline{intBlink} task is sent to the device (\cref{lst:intro_liftmtask}) and, in parallel, an editor is shown that updates the value of the interval \gls{SDS} (\cref{lst:intro_editor}).
-To allow ending the task, the \gls{ITASK} task ends with a sequential operation that returns a constant value when the button is pressed, making the task stable.
+To illustrate \imtask{}, an example application is shown.
+The application is an interactive application for blinking \pgls{LED} on the microcontroller at a certain frequency that can be set and updated at run time.
+\Cref{lst:intro_blink,fig:intro_blink} show the \gls{ITASK} part of the code and a screenshot.
+Using \cleaninline{enterInformation}, the connection specification of the \gls{TCP} device is queried through a web editor (\cref{lst:intro_enterDevice,fig:intro_blink_dev}).
+\Cref{lst:intro_withshared} defines \pgls{SDS} to communicate the blinking interval between the server and the edge device.
+The \gls{MTASK} device is connected using \cleaninline{withDevice} at \cref{lst:intro_withdevice}.
+Once connected, the \cleaninline{intBlink} task is sent to the device (\cref{lst:intro_liftmtask}) and, in parallel, a web editor is shown that updates the value of the interval \gls{SDS} (\cref{lst:intro_editor,fig:intro_blink_int}).
+To allow terminating of the task, the \gls{ITASK} task ends with a sequential operation that returns a constant value when the button is pressed, making the task stable.
\cleaninputlisting[firstline=10,lastline=18,numbers=left,caption={The \gls{ITASK} code for the interactive blinking application.},label={lst:intro_blink}]{lst/blink.icl}
\begin{subfigure}{.5\textwidth}
\centering
\includegraphics[width=.9\linewidth]{blink1g}
- \caption{Device selection.}
+ \caption{Device selection.}\label{fig:intro_blink_dev}
\end{subfigure}%
\begin{subfigure}{.5\textwidth}
\centering
\includegraphics[width=.9\linewidth]{blink2g}
- \caption{Changing the interval.}
+ \caption{Changing the interval.}\label{fig:intro_blink_int}
\end{subfigure}
\caption{The \gls{UI} for the interactive blink application in \gls{MTASK}.}%
\label{fig:intro_blink}
It has its own tasks, \glspl{SDS}, and \gls{UOD}.
This task first defines \gls{GPIO} pin 13 to be of the output type (\cref{lst:intro:declarePin}), followed by lifting the \gls{ITASK} \gls{SDS} to an \gls{MTASK} \gls{SDS} (\cref{lst:intro:liftsds}).
The main expression of the program calls the \cleaninline{blink} function with an initial state.
-This function on \crefrange{lst:intro:blink_fro}{lst:intro:blink_to} first reads the interval \gls{SDS}, waits the specified delay, writes the state to the \gls{GPIO} pin and calls itself recursively using the inverse of the state.
+This function on \crefrange{lst:intro:blink_fro}{lst:intro:blink_to} first reads the interval \gls{SDS}, waits the specified delay, writes the state to the \gls{GPIO} pin, and calls itself recursively using the inverse of the state in order to run continuously.
\begin{lstClean}[numbers=left,belowskip=0pt]
intBlink :: (Shared sds Int) -> Main (MTask v Int) | mtask v & ...\end{lstClean}
-\cleaninputlisting[aboveskip=0pt,firstnumber=3,firstline=22,numbers=left,caption={The \gls{MTASK} code for the interactive blinking application.},label={lst:intro_blink_mtask}]{lst/blink.icl}
+\cleaninputlisting[aboveskip=0pt,firstnumber=4,firstline=23,numbers=left,caption={The \gls{MTASK} code for the interactive blinking application.},label={lst:intro_blink_mtask}]{lst/blink.icl}
\subsection{Other \texorpdfstring{\glsxtrshort{TOP}}{TOP} languages}
-While \gls{ITASK} conceived \gls{TOP}, it is not the only \gls{TOP} system.
-Some \gls{TOP} systems arose from Master's and Bachelor's thesis projects.
-For example, \textmu{}Task \citep{piers_task-oriented_2016}, a \gls{TOP} language for modelling non-interruptible embedded systems in \gls{HASKELL}, and LTasks \citep{van_gemert_task_2022}, a \gls{TOP} language written in the dynamically typed programming language {LUA}.
+While \gls{ITASK} conceived \gls{TOP}, it is no longer the only \gls{TOP} system.
Some \gls{TOP} languages were created to fill a gap encountered in practise.
-Toppyt \citep{lijnse_toppyt_2022} is a general purpose \gls{TOP} language written in \gls{PYTHON} used to host frameworks for modelling \emph{Command\&Control} systems, and hTask \citep{lubbers_htask_2022}, a vessel for experimenting with asynchronous \glspl{SDS}.
-Finally there are \gls{TOP} languages with strong academic foundations.
+Toppyt \citep{lijnse_toppyt_2022} is a general purpose \gls{TOP} language written in \gls{PYTHON} used to host frameworks for modelling \emph{command \& control} systems, and hTask \citep{lubbers_htask_2022}, a vessel for experimenting with asynchronous \glspl{SDS}.
+Furthermore, some \gls{TOP} systems arose from Master's and Bachelor's thesis projects.
+For example, \textmu{}Task \citep{piers_task-oriented_2016}, a \gls{TOP} language for modelling non-interruptible embedded systems in \gls{HASKELL}, and LTasks \citep{van_gemert_task_2022}, a \gls{TOP} language written in the dynamically typed programming language {LUA}.
+Finally, there are \gls{TOP} languages with strong academic foundations.
\Gls{TOPHAT} is a fully formally specified \gls{TOP} language designed to capture the essence of \gls{TOP} formally \citep{steenvoorden_tophat_2019}.
Such a formal specification allows for symbolic execution, hint generation, but also the translation to \gls{ITASK} for actually performing the work \citep{steenvoorden_tophat_2022}.
\Citeauthor{steenvoorden_tophat_2022} distinguishes two instruments for \gls{TOP}: \gls{TOP} languages and \gls{TOP} engines.
This section provides a thorough overview of the relation between the scientific publications and the contents of this thesis.
\subsection{\Fullref{prt:dsl}}
-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.
+The \gls{MTASK} system is an \gls{EDSL} and during the development of it, several novel basal techniques for embedding \glspl{DSL} in \gls{FP} languages have been found.
This paper-based episode contains the following papers:
\begin{enumerate}
\item \emph{Deep Embedding with Class} \citep{lubbers_deep_2022} is the basis for \cref{chp:classy_deep_embedding}.
It shows a novel deep embedding technique for \glspl{DSL} where the resulting language is extendible both in constructs and in interpretation just using type classes and existential data types.
The related work section is updated with the research found after publication.
\Cref{sec:classy_reprise} was added after publication and contains a (yet) unpublished extension of the embedding technique for reducing the required boilerplate at the cost of requiring some advanced type system extensions.
- \item \emph{First-Class Data Types in Shallow Embedded Domain-Specific Languages} \citep{lubbers_first-class_2022}\label{enum:first-class} is the basis for \cref{chp:first-class_datatypes}.
+ \item \emph{First-\kern-1ptClass Data Types in Shallow Embedded Domain-Specific Languages} \citep{lubbers_first-class_2022}\label{enum:first-class} is the basis for \cref{chp:first-class_datatypes}.
It shows how to inherit data types from the host language in \glspl{EDSL} using metaprogramming by providing a proof-of-concept implementation using \gls{HASKELL}'s metaprogramming system: \glsxtrlong{TH}.
The paper also serves as a gentle introduction to, and contains a thorough literature study on \glsxtrlong{TH}.
\end{enumerate}
\paragraph{Other publications on \texorpdfstring{\glspl{EDSL}}{eDSLs}:}
-Furthermore, I co-authored another paper that is worth mentioning but is not part of the \gls{MTASK} system yet and hence not part of the dissertation.
+Furthermore, I co-authored a paper that is not part of the \gls{MTASK} system yet and hence not part of the dissertation.
\begin{enumerate}[resume]
- \item \emph{Strongly-Typed Multi-View Stack-Based Computations} \citep{koopman_strongly-typed_2022}\label{enum:stack-based} shows how to create type-safe \glspl{EDSL} representing stack-based computations.
+ \item \emph{Strongly-Typed Multi-\kern-2.5ptView Stack-\kern-1.25ptBased Computations} \citep{koopman_strongly-typed_2022}\label{enum:stack-based} shows how to create type-safe \glspl{EDSL} representing stack-based computations.
Instead of encoding the arguments to a function as arguments in the host language, stack-based approaches use a run time stack that contains the arguments.
By encoding the required contents of the stack in the types, such systems can be made type safe.
\end{enumerate}
\paragraph{Contribution:}
The papers of which I am first author are solely written by me, there were weekly meetings with co-authors in which we discussed and refined the ideas.
-\subsection{\Fullref{prt:top}}
+\subsection{\crtCref{prt:top}: \hspace{8.28992pt}\nameref{prt:top}}
This episode is a monograph that shows the design, properties, implementation and usage of the \gls{MTASK} system and \gls{TOP} for the \gls{IOT}.
It is compiled from the following publications:
\begin{enumerate}[resume]
- \item \emph{A Task-Based \glsxtrshort{DSL} for Microcomputers} \citep{koopman_task-based_2018}
+ \item \emph{A Task-\kern-1.25ptBased \glsxtrshort{DSL} for Microcomputers} \citep{koopman_task-based_2018}
is the initial \gls{TOP}\slash{}\gls{MTASK} paper.
It provides an overview of the initial \gls{TOP} \gls{MTASK} language and shows first versions of some interpretations.
\item \emph{Task Oriented Programming for the Internet of Things} \citep{lubbers_task_2018}\footnotetext{This work is an extension of my Master's thesis \citep{lubbers_task_2017}.}
shows how a simple imperative variant of \gls{MTASK} was integrated with \gls{ITASK}.
- While the language was a lot different from later versions, the integration mechanism is still used in \gls{MTASK} today.
+ While the language differs a lot from the current version, the integration mechanism is still used.
% \paragraph{Contribution}
% 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.
\item \emph{Multitasking on Microcontrollers using Task Oriented Programming} \citep{lubbers_multitasking_2019}\footnote{This work acknowledges the support of the \erasmusplus{} project ``Focusing Education on Composability, Comprehensibility and Correctness of Working Software'', no.\ 2017--1--SK01--KA203--035402.}
is a short paper on the multitasking capabilities of \gls{MTASK} comparing it to traditional multitasking methods for \gls{ARDUINO}.
% \paragraph{Contribution}
% The research in this paper and writing the paper was performed by me, though there were weekly meetings with Pieter Koopman and Rinus Plasmeijer.
- \item \emph{Simulation of a Task-Based Embedded Domain Specific Language for the Internet of Things} \citep{koopman_simulation_2018}\footnotemark[\value{footnote}]
- are the revised lecture notes for a course on the \gls{MTASK} simulator was provided at the 2018 \gls{CEFP}\slash{}\gls{3COWS} winter school in Ko\v{s}ice, Slovakia, January 22--26, 2018.
+ \item \emph{Simulation of a Task-\kern-1.25ptBased Embedded Domain Specific Language for the Internet of Things} \citep{koopman_simulation_2023}\footnotemark[\value{footnote}]
+ are the revised lecture notes for a course on the \gls{MTASK} simulator provided at the 2018 \gls{CEFP}\slash{}\gls{3COWS} winter school in Ko\v{s}ice, Slovakia, January 22--26, 2018.
% \paragraph{Contribution}
% Pieter Koopman wrote and taught it, I helped with the software and research.
- \item \emph{Writing Internet of Things Applications with Task Oriented Programming} \citep{lubbers_writing_2019}\footnotemark[\value{footnote}]
+ \item \emph{Writing Internet of Things Applications with Task Oriented Programming} \citep{lubbers_writing_2023}\footnotemark[\value{footnote}]
are the revised lecture notes from a course on programming \gls{IOT} systems using \gls{MTASK} provided at the 2019 \gls{CEFP}\slash{}\gls{3COWS} summer school in Budapest, Hungary, June 17--21, 2019.
% \paragraph{Contribution}
% Pieter Koopman prepared and taught half of the lecture and supervised the practical session.
\end{enumerate}
\paragraph{Contribution:}
-The original imperative predecessors, the \gls{MTASK} language, and their initial interpretations were developed by Pieter Koopman and Rinus Plasmeijer.
-I continued with the language; developed the byte code interpreter, the precursor to the \gls{C} code generation interpretation; the integration with \gls{ITASK}; and the \gls{RTS}.
-The paper of which I am first author are solely written by me, there were weekly meetings with the co-authors in which we discussed and refined the ideas.
+The original \gls{MTASK} language, and their initial interpretations were developed by Pieter Koopman and Rinus Plasmeijer.
+I extended the language, developed the byte code interpreter, the integration with \gls{ITASK}, and the \gls{RTS}.
+The papers of which I am first author are solely written by me, there were weekly meetings with the co-authors in which we discussed and refined the ideas.
-\subsection{\nameref{prt:tvt}}
-\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.
+\subsection{\Fullref{prt:tvt}}
+\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}.
This chapter is based on the conference paper and a journal paper extending it:
\begin{enumerate}[resume]
- \item \emph{Tiered versus Tierless IoT Stacks: Comparing Smart Campus Software Architectures} \citep{lubbers_tiered_2020}\footnote{This work was partly funded by the 2019 Radboud-Glasgow Collaboration Fund.}\label{enum:iot20} compares traditional tiered programming to tierless architectures by comparing two implementations of a smart-campus application.
+ \item \emph{Tiered versus Tierless \glsxtrshort{IOT} Stacks: Comparing Smart Campus Software Architectures} \citep{lubbers_tiered_2020}\footnote{This work was partly funded by the 2019 Radboud-Glasgow Collaboration Fund.}\label{enum:iot20} compares traditional tiered programming to tierless architectures by comparing two implementations of a smart-campus application.
\item \emph{Could Tierless Programming Reduce IoT Development Grief?} \citep{lubbers_could_2022}
is an extended version of paper~\ref{enum:iot20}.
It compares programming traditional tiered architectures to tierless architectures by illustrating a qualitative and a quantitative four-way comparison of a smart-campus application.
\paragraph{Contribution:}
Writing the paper was performed by all authors.
I created the server application, the \cimtask{} implementation (\glsxtrshort{CWS}), and the \citask{} implementation (\glsxtrshort{CRS});
-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}.
+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}.
\input{subfilepostamble}
\end{document}
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