\section{Introduction}
\Gls{IoT} technology is emerging rapidly. It offers myriads of solutions
and transforms the way we interact with technology.

Initially the term was coined to describe \gls{RFID} devices and the
communication between them. However, currently the term \gls{IoT} encompasses
all small devices that communicate with each other and the world. These devices
are often equipped with sensors, \gls{GNSS} modules\footnote{e.g.\ the American
\gls{GPS} or the Russian \gls{GLONASS}.} and
actuators~\cite{da_xu_internet_2014}. With these new technologies information
can be tracked accurately using little power and bandwidth. Moreover, \gls{IoT}
technology is coming into people's homes, clothes and
healthcare~\cite{riazul_islam_internet_2015}. For example, for a few euros a
consumer ready fitness tracker watch can be bought that tracks heartbeat and
respiration levels.

The \gls{TOP} paradigm and the corresponding \gls{iTasks} implementation offer
a high abstraction level for real world workflow
tasks~\cite{plasmeijer_itasks:_2007}. These workflow tasks can be described
through an \gls{EDSL} and modeled as \glspl{Task}. The system will generate a
multi-user web app from the specification. This web service can be accessed
through a browser and is used to complete these \glspl{Task}. Familiar workflow
patterns like sequential, parallel and conditional \glspl{Task} can be modelled
using combinators.

\gls{iTasks} has proven to be useful in many fields of operation such as
incident management~\cite{lijnse_top_2013}. Interfaces are automatically
generated for the types of data which makes rapid development possible.
\Glspl{Task} in the \gls{iTasks} system are modelled after real life workflow
tasks but the modelling is applied on a high level. Therefore it is difficult
to connect \gls{iTasks}-\glspl{Task} to real world \glspl{Task} and allow them
to interact. A lot of the actual tasks could be performed by small \gls{IoT}
devices. Nevertheless, adding such devices to the current system is difficult
to say the least as it was not designed to cope with these devices. 

In the current system such adapters connecting devices to \gls{iTasks} --- in
principle --- can be written as \glspl{SDS}\footnote{Similar as to resources
such as time are available in the current \gls{iTasks} implementation.}.
However, this requires a very specific adapter to be written for every device
and function.  This forces a fixed logic in the device that is set at compile
time. Many small \gls{IoT} devices have limited processing power but are still
powerful enough for decision making. Recompiling the code for a small
\gls{IoT} device is expensive and therefore it is difficult to use a device
dynamically for multiple purposes. Oortgiese et al.\ lifted \gls{iTasks} from a
single server model to a distributed server architecture that is also runnable
on small devices such as those powered by
\gls{ARM}~\cite{oortgiese_distributed_2017}. However, this is limited to
fairly high performance devices that are equipped with high speed communication
channels because it requires the device to run the entire \gls{iTasks} core.
Devices in \gls{IoT} often have only Low Throughput Network communication with
low bandwidth and a very limited amount of processing power and are therefore
not suitable to run an entire \gls{iTasks} core.

\section{Problem statement}
The updates to the \gls{mTask}-system~\cite{koopman_type-safe_nodate} will
bridge this gap in the current system by introducing a new communication
protocol, device application and \glspl{Task} synchronizing the two. The system
can run on devices as small as \gls{Arduino}
microcontrollers~\cite{noauthor_arduino_nodate} and operates via the same
paradigms and patterns as regular \glspl{Task} in the \gls{TOP} paradigm.
Devices in the \gls{mTask}-system can run small imperative programs written in
an \gls{EDSL} and have access to \glspl{SDS}. \Glspl{Task} are sent to the
device at runtime, avoiding recompilation and thus write cycles on the program
memory.

\section{Document structure}
The structure of this thesis is as follows.

Chapter~\ref{chp:introduction} contains the problem statement, motivation,
related work and the structure of the document.
Chapter~\ref{chp:top} introduces the reader to the basics of \gls{TOP} and
\gls{iTasks}.
Chapter~\ref{chp:dsl} discusses the pros and cons of different embedding
methods to create \gls{EDSL}.
Chapter~\ref{chp:mtask} shows the existing \gls{mTask}-\gls{EDSL} on which is
extended upon in this dissertation.
Chapter~\ref{chp:mtaskcont} describes the view and functionality for
the \gls{mTask}-\gls{EDSL} that were added and used in the system.
Chapter~\ref{chp:arch} shows the architecture used for \gls{IoT}-devices that
are a part of the new \gls{mTask}-system. It covers the client software running
on the device and the server written in \gls{iTasks}.
Chapter~\ref{chp:conclusion} concludes by answering the research questions
and discusses future research.
Appendix~\ref{app:communication-protocol} shows the concrete protocol used for
communicating between the server and client.
Appendix~\ref{app:device-interface} shows the concrete interface for the
devices.

Text written using the \CI{Teletype} font indicates code and is often
referring to a listing. \emph{Emphasized} text is used for proper nouns and
words that have a unexpected meaning.

The complete source code of this thesis can be found in the following git
repository:\\
\url{https://git.martlubbers.net/msc-thesis1617.git}

The complete source code of the \gls{mTask}-system can be found in the
following git repository:
\url{https://git.martlubbers.net/mTask.git}

\section{Related work}
Similar research has been conducted on the subject.
For example, microcontrollers such as the \gls{Arduino} can be remotely
controlled by the \gls{Firmata}-protocol\footnote{``firmata/protocol:
Documentation of the Firmata protocol.''
(\url{https://github.com/firmata/protocol}). [Accessed: 23-May-2017].}. This
protocol is designed to expose the peripherals such as sensors to the server.
This allows very fine grained control but with the cost of excessive
communication overhead since no code is executed on the device, only the
peripherals are queried. A \gls{Haskell} implementation of the protocol is
also available\footnote{``hArduino by LeventErkok.'' (\url{%
https://leventerkok.github.io/hArduino}). [Accessed: 23-May-2017].}.

\Gls{Clean} has a history of interpretation and there is a lot of research
happening on the intermediate language \gls{SAPL}. \Gls{SAPL} is a purely
functional intermediate language that has interpreters written in
\gls{C++}~\cite{jansen_efficient_2007}, \gls{Javascript}%
~\cite{domoszlai_implementing_2011} and \gls{Clean} and \gls{Haskell} compiler
backends~\cite{domoszlai_compiling_2012}. However, interpreting the resulting
code is still heap-heavy and therefore not directly suitable for devices with
as little as $2K$ of RAM such as the \gls{Arduino} \emph{Uno}. It might be
possible to compile the \gls{SAPL} code into efficient machine language or
\gls{C} but then the system would lose its dynamic properties since the
microcontroller then would have to be reprogrammed every time a new \gls{Task}
is sent to the device.

\Glspl{EDSL} have often been used to generate \gls{C} code for microcontroller
environments. This work uses parts of the existing \gls{mTask}-\gls{EDSL} which
generates \gls{C} code to run a \gls{TOP}-like system on microcontrollers%
~\cite{plasmeijer_shallow_2016}~\cite{koopman_type-safe_nodate}.  Again, this
requires a reprogramming cycle every time the \gls{Task}-specification is
changed.

Another \gls{EDSL} designed to generate low-level high-assurance programs is
called \gls{Ivory} and uses \gls{Haskell} as a host language%
~\cite{elliott_guilt_2015}. The language uses the \gls{Haskell} type-system to
make unsafe languages type safe. For example, \gls{Ivory} has been used in the
automotive industry to program parts of an autopilot%
~\cite{pike_programming_2014}~\cite{hickey_building_2014}. \Gls{Ivory}'s syntax
is deeply embedded but the type system is shallowly embedded. This requires
several \gls{Haskell} extensions that offer dependent type constructions. The
process of compiling an \gls{Ivory} program happens in stages. The embedded
code is transformed into an \gls{AST} that is sent to a backend. In the new
system, the \gls{mTask}-\gls{EDSL} transforms the embedded code during
compile-time directly into the backend which is often a state transformer that
will execute on runtime.
