\section{Discussion \& Future Research}
-The system is still a crude prototype and a proof of concept. Improvements and
-extension for the system are amply available in several fields of study.
-
-\subsection{Simulation}
-An additional simulation view to the \gls{mTask}-\gls{EDSL} could be added that
-works in the same way as the existing \gls{C}-backed simulation. It simulates
-the bytecode interpretation. Moreover would be possible to let the simulator
-function as a real device, thus handling all communication through the
-existing \gls{SDS}-based systems and behave like a real device. At the moment
-the \emph{POSIX}-client is the reference client and contains debugging code.
-Adding a simulation view to the system allows for easy interactive debugging.
-However, it might not be easy to devise a simulation tool that accurately
-simulates the \gls{mTask} system accurately on some levels. The semantics can
-be simulated but timing and peripheral input/output are more difficult to
-simulate properly.
-
-\subsection{Optimization}
-\paragraph{Multitasking on the client:}
-True multitasking could be added to the client software. This allows
-\gls{mTask}-\glspl{Task} to run truly parallel. All \glspl{mTask} get slices
-of execution time and will each have their own interpreter state instead of one
-system-wide one that is reset after am \gls{mTask} finishes. This does require
-separate stacks for each \gls{Task} and therefore increases the system
-requirements of the client software. However, it could be implemented as a
-compile-time option and exchanged during the handshake so that the server knows
-the multithreading capabilities of the client.
-
-\paragraph{Optimizing the interpreter:}
-Hardly any work has been done in the interpreter. The current interpreter is a
-no nonsense stack machine. A lot of improvements can be done in this part. For
-example, precomputed \emph{gotos} can improve jumping to the correct part of
-the code corresponding to the correct instruction. Moreover, the stack
-currently consists of 16-bit values. All operations work on 16-bit values and
-this simplifies the interpreter implementation. A memory improvement can be
-made by converting the stack to 8-bit values. This does pose some problems
-since an equality instruction must work on single-byte booleans \emph{and}
-two-byte integers. Adding specialized instructions per word size could overcome
-this problem.
-
-\subsection{Resources}
-\paragraph{Resource analysis: }
-Resource analysis during compilation can be useful to determine if an
-\gls{mTask}-\gls{Task} is suitable for a specific device. If the device does
-not contain the correct peripherals --- such as an \gls{LCD} --- then the
-\gls{mTask}-\gls{Task} should be rejected and feedback to the user must be
-given. It might even be possible to do this statically on the type level.
-
-\paragraph{Extended resource analysis: }
-The previous idea could be extended to the analysis of stack size and possibly
-communication bandwidth. With this functionality ever more reliable fail-over
-systems can be designed. When the system knows precise bounds it can allocate
-more \glspl{Task} on a device whilst staying within safe memory bounds. The
-resource allocation can be done at runtime within the backend itself or a
-general backend can be devices that can calculate the resources needed for a
-given \gls{mTask}. A specific \gls{mTask} cannot have multiple views at the
-same time due to the restrictions of class based shallow embedding. It might
-even be possible to encode the resource allocation in the type system itself
-using forms of dependant types.
-
-\subsection{Functionality}
-\paragraph{Add more combinators: }
-More \gls{Task}-combinators --- already existing in the \gls{iTasks}-system ---
-could be added to the \gls{mTask}-system to allow for more fine-grained control
-flow between \gls{mTask}-\glspl{Task}. In this way the new system follows the
-\gls{TOP} paradigm even more and makes programming \glspl{mTask} for
-\gls{TOP}-programmers more seamless. Some of the combinators require previously
-mentioned extension such as the parallel combinator. Others might be achieved
-using simple syntactic transformations.
-
-\paragraph{Launch \glspl{Task} from a \gls{Task}: }\label{par:tasklaunch}
-Currently the \gls{C}-view allows \glspl{Task} to launch other \glspl{Task}. In
-the current system this type of logic has to take place server side. Adding
-this functionality to the bytecode-view allows greater flexibility, easier
-programming and less communication resources. Adding these semantics requires
-modifications to the client software and extensions to the communication
-protocol since relations between \glspl{Task} also need to be encoded and
-communicated.
-
-The \gls{SDS} functionality in the current system is bare. There is no easy way
-of reusing a \gls{SDS} for another \gls{Task} on the same device or on another
-device. Such functionality can be implemented in a crude way by tying the
-\glspl{SDS} together in the \gls{iTasks} environment. However, this will result
-in a slow updating system. Functionality for reusing shares from a device
-should be added. This requires rethinking the storage because some typedness is
-lost when the \gls{SDS} is stored after compilation. A possibility would be to
-use runtime typing with \CI{Dynamic}s or the encoding technique currently used
-for \CI{BCValue}s. Using \glspl{SDS} for multiple \glspl{Task} within one
-device is solved when the previous point at paragraph~\ref{par:tasklaunch} is
-implemented.
-
-\subsection{Robustness}
-\paragraph{Reconnect with lost devices:}
-The robustness of the system can be greatly improved. Devices that lose
-connection are in the current system not well supported. The device will stop
-functioning and have to be emptied for a reconnect. \Glspl{Task} residing on a
-device that disconnected should be kept on the server to allow a swift
-reconnect and restoration of the \glspl{Task}. This holds the same for the
-client software. The client drops all existing \glspl{Task} on a shutdown
-request. An extra specialization of the shutdown could be added that drops the
-connection but keeps the \glspl{Task} in memory. During the downtime the
-\glspl{Task} can still be executed but publications need to be delayed. If the
-same server connects to the client the delayed publications can be sent
-anyways.
-
-\paragraph{Reverse \gls{Task} sending:}
-Moreover, devices could send their current \glspl{Task} back at the
-server to synchronize it. This allows interchanging servers without
-interrupting the client. Allowing the client to send \glspl{Task} to the server
-is something to handle with care because it can easily cause high bandwidth
-usage.
+\input{conclusion.discussion}
\section{Conclusion}
-This thesis introduces a novel system for add \gls{IoT} functionality to
-the \gls{TOP} implementation \gls{iTasks}. A new view for the existing
-\gls{mTask}-\gls{EDSL} has been created which compiles the program
-into bytecode that can be interpreted by a client. Clients have
-been written for several microcontrollers and consumer architectures which can
-be connected through various means of communication such as serial port,
-bluetooth, wifi and wired network communication. The bytecode on the devices is
-interpreted using a stack machine and provides the programmer interfaces
-to the peripherals. The semantics of the \glspl{mTask} tries to resemble the
-\gls{iTasks} semantics as close as possible.
-
-The host language has a very efficient compiler and code generator. Therefore,
-compiling \glspl{mTask} is also fast. Compiling \glspl{mTask} is nothing
-more than running some functions native to the host language.
-
-The dynamic nature allows the microcontroller to be programmed once and used
-many times. The program memory of microcontrollers often guarantees around
-$10.000$ write or upload cycles and therefore existing techniques such as
-generating \gls{C} code are not usable for dynamic \gls{Task} environments.
-The dynamic nature also allows the programmer to design fail-over mechanisms.
-When a device is assigned a \gls{Task} but another device suddenly becomes
-unusable, the \gls{iTasks} system can reassign a new \gls{mTask}-\gls{Task} to
-another device that is also suitable for running the \gls{Task} without needing
-to recompile the code.
+\input{conclusion.conclusion}
repositories / msc-thesis1617.git / blobdiff