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[msc-thesis1617.git] / methods.top.tex

diff --git a/methods.top.tex b/methods.top.tex
index 174a783..ec330c9 100644 (file)
--- a/methods.top.tex
+++ b/methods.top.tex
@@ -1,10 +1,9 @@
-\section{\acrlong{TOP}}
-\subsection{\gls{iTasks}}
-\gls{TOP} is a recent programming paradigm implemented as
+\section{iTasks}
+\gls{TOP} is a modern recent programming paradigm implemented as

 \gls{iTasks}\cite{achten_introduction_2015} in the pure lazy functional
 language \gls{Clean}\cite{brus_cleanlanguage_1987}. \gls{iTasks} is a
 \gls{iTasks}\cite{achten_introduction_2015} in the pure lazy functional
 language \gls{Clean}\cite{brus_cleanlanguage_1987}. \gls{iTasks} is a

-\gls{EDSL} to model workflow tasks in the broadest sense. A \CI{Task} is just
-a function that, given some state, returns the observable \CI{TaskValue}. The
+\gls{EDSL} to model workflow tasks in the broadest sense. A \gls{Task} is just
+a function that --- given some state --- returns the observable \CI{TaskValue}. The

 \CI{TaskValue} of a \CI{Task} can have different states. Not all state
 transitions are possible as shown in Figure~\ref{fig:taskvalue}. Once a value
 is stable it can never become unstable again. Stability is often reached
 \CI{TaskValue} of a \CI{Task} can have different states. Not all state
 transitions are possible as shown in Figure~\ref{fig:taskvalue}. Once a value
 is stable it can never become unstable again. Stability is often reached


@@ -20,7 +19,7 @@ image in the \CI{NoValue} state, the second image does not have all the fields
 filled in and therefore the \CI{TaskValue} remains \CI{Unstable}. In the third
 image all fields are entered and the \CI{TaskValue} transitions to the
 \CI{Unstable} state. When the user presses \emph{Continue} the value becomes
 filled in and therefore the \CI{TaskValue} remains \CI{Unstable}. In the third
 image all fields are entered and the \CI{TaskValue} transitions to the
 \CI{Unstable} state. When the user presses \emph{Continue} the value becomes

-\CI{Stable} and can not be changed any further.
+\CI{Stable} and cannot be changed any further.

 
 \begin{figure}[H]
        \centering
 
 \begin{figure}[H]
        \centering


@@ -28,7 +27,7 @@ image all fields are entered and the \CI{TaskValue} transitions to the
        \caption{The states of a \CI{TaskValue}}\label{fig:taskvalue}
 \end{figure}
 
        \caption{The states of a \CI{TaskValue}}\label{fig:taskvalue}
 \end{figure}
 

-\begin{lstlisting}[language=Clean,label={lst:taskex},%
+\begin{lstlisting}[label={lst:taskex},%

        caption={An example \gls{Task} for entering a name}]
 :: Name = { firstname :: String
           , lastname  :: String
        caption={An example \gls{Task} for entering a name}]
 :: Name = { firstname :: String
           , lastname  :: String


@@ -43,6 +42,7 @@ enterName = enterInformation "Enter your name" []
 \end{lstlisting}
 
 \begin{figure}[H]
 \end{lstlisting}
 
 \begin{figure}[H]

+       \centering

        \begin{subfigure}{.25\textwidth}
                \centering
                \includegraphics[width=.9\linewidth]{taskex1}
        \begin{subfigure}{.25\textwidth}
                \centering
                \includegraphics[width=.9\linewidth]{taskex1}


@@ -61,24 +61,25 @@ enterName = enterInformation "Enter your name" []
        \caption{Example of a generated user interface}
 \end{figure}
 
        \caption{Example of a generated user interface}
 \end{figure}
 

-For a type to be suitable it must have instances for a collection of generic
-functions that are captured in the class \CI{iTask}. Basic types have
+For a type to be suitable, it must have instances for a collection of generic
+functions that is captured in the class \CI{iTask}. Basic types have

 specialization instances for these functions and show an according interface.
 Generated interfaces can be modified with decoration operators.
 
 specialization instances for these functions and show an according interface.
 Generated interfaces can be modified with decoration operators.
 

-\subsection{Combinators}
+\section{Combinators}

 \Glspl{Task} can be combined using so called \gls{Task}-combinators.
 Combinators describe relations between \glspl{Task}. \Glspl{Task} can be
 combined in parallel, sequenced and their result values can be converted to
 \Glspl{Task} can be combined using so called \gls{Task}-combinators.
 Combinators describe relations between \glspl{Task}. \Glspl{Task} can be
 combined in parallel, sequenced and their result values can be converted to

-\glspl{SDS}. Moreover, a very important combinator is the step combinator that
-starts a new task according to the \CI{TaskValue}. The type signatures of the
-basic combinators are shown in Listing~\ref{lst:combinators}.
+\glspl{SDS}. Moreover, a very important combinator is the step combinator which
+starts a new task according to specified predicates on the \CI{TaskValue}.
+Type signatures of the basic combinators are shown in
+Listing~\ref{lst:combinators}.

 
 \begin{itemize}
        \item Step:
 
                The step combinator is used to start \glspl{Task} when a predicate on
 
 \begin{itemize}
        \item Step:
 
                The step combinator is used to start \glspl{Task} when a predicate on

-               the \CI{TaskValue} holds or an action has been taken place. The bind
+               the \CI{TaskValue} holds or an action has taken place. The bind

                operator can be written as a step combinator.
                \begin{lstlisting}[language=Clean]
 (>>=) infixl 1 :: (Task a) (a -> (Task b)) -> (Task b) | iTask a & iTask b
                operator can be written as a step combinator.
                \begin{lstlisting}[language=Clean]
 (>>=) infixl 1 :: (Task a) (a -> (Task b)) -> (Task b) | iTask a & iTask b


@@ -87,8 +88,8 @@ basic combinators are shown in Listing~\ref{lst:combinators}.
         onValue (Value a _)     = Just (f a)
         onValue _               = Nothing
 
         onValue (Value a _)     = Just (f a)
         onValue _               = Nothing
 

-               onStable (Value a True) = Just (f a)
-               onStable _              = Nothing
+        onStable (Value a True) = Just (f a)
+        onStable _              = Nothing

                \end{lstlisting}
        \item Parallel:
 
                \end{lstlisting}
        \item Parallel:
 


@@ -98,7 +99,7 @@ basic combinators are shown in Listing~\ref{lst:combinators}.
                dictates.
 \end{itemize}
 
                dictates.
 \end{itemize}
 

-\begin{lstlisting}[language=Clean,%
+\begin{lstlisting}[%

        caption={\Gls{Task}-combinators},label={lst:combinators}]
 //Step combinator
 (>>*)  infixl 1 :: (Task a) [TaskCont a (Task b)] -> Task b     | iTask a & iTask b
        caption={\Gls{Task}-combinators},label={lst:combinators}]
 //Step combinator
 (>>*)  infixl 1 :: (Task a) [TaskCont a (Task b)] -> Task b     | iTask a & iTask b


@@ -117,5 +118,70 @@ basic combinators are shown in Listing~\ref{lst:combinators}.
 (-&&-) infixr 4 :: (Task a) (Task b)              -> Task (a,b) | iTask a & iTask b
 \end{lstlisting}
 
 (-&&-) infixr 4 :: (Task a) (Task b)              -> Task (a,b) | iTask a & iTask b
 \end{lstlisting}
 

-\subsection{\acrlongpl{SDS}}
+\section{Shared Data Sources}
+\Glspl{SDS} are an abstraction over resources that are available in the world
+or in the \gls{iTasks} system. The shared data can be a file on disk, the
+system time, a random integer or just some data stored in memory. The actual
+\gls{SDS} is just a record containing functions on how to read and write the
+source. In these functions the \CI{*IWorld} --- which in turn contains the real
+program \CI{*World} --- is available. Accessing the outside world is required
+for interacting with it and thus the functions can access files on disk, raw
+memory, other shares and hardware.
+
+The basic operations for \glspl{SDS} are get, set and update. The signatures
+for these functions are shown in Listing~\ref{lst:shares}. By default, all
+shares are files containing a \gls{JSON} encoded version of the object and thus
+are persistent between restarts of the program. Library functions for shares
+residing in memory are available as well. The three main operations on shares
+are atomic in the sense that during reading no other tasks are executed. The
+system provides useful functions to transform, map and combine \glspl{SDS}
+using combinators. The system also provides functionality to inspect the value
+of a \gls{SDS} and act upon a change. \Glspl{Task} waiting on a \gls{SDS} to
+change are notified when needed. This results in low resource usage because
+\glspl{Task} are never constantly inspecting \gls{SDS} values but are notified.
+
+\begin{lstlisting}[%
+       label={lst:shares},caption={\Gls{SDS} functions}]
+:: RWShared p r w = ... 
+:: ReadWriteShared r w :== RWShared () r w
+:: ROShared p r :== RWShared p () r
+:: ReadOnlyShared r :== ROShared () r
+
+:: Shared r :== ReadWriteShared r r
+
+get ::          (ReadWriteShared r w)           -> Task r | iTask r
+set :: w        (ReadWriteShared r w)           -> Task w | iTask w
+upd :: (r -> w) (ReadWriteShared r w)           -> Task w | iTask r & iTask w
+
+sharedStore :: String a -> Shared a | JSONEncode{|*|}, JSONDecode{|*|}
+\end{lstlisting}

 
 

+\section{Parametric Lenses}
+\Glspl{SDS} can contain complex data structures such as lists, trees and even
+resources in the outside world. Sometimes, an update action only updates a part
+of the resource. When this happens, all waiting \glspl{Task} looking at the
+resource are notified of the update. However, it may be the case that
+\glspl{Task} where only looking at parts of the structure that was not updated.
+To solve this problem, parametric lenses were
+introduced~\cite{domoszlai_parametric_2014}.
+
+Parametric lenses add a type variable to the \gls{SDS} that is in the current
+library functions fixed to \CI{()}. When a \gls{SDS} executes a write
+operation it also provides the system with a notification predicate. This
+notification predicate is a function \CI{p -> Bool} where \CI{p} is the
+parametric lens type. This allows programmers to create a big share, and have
+\glspl{Task} only look at parts of the big share. This technique is used in the
+current system in memory shares. The \CI{IWorld} contains a map that is
+accessible through an \gls{SDS}. While all data is stored in the map, only
+\glspl{Task} looking at a specific entry are notified when the structure is
+updated. The type of the parametric lens is the key in the map.
+
+Functionality for setting parameters is added in the system. The most important
+function is the \CI{sdsFocus} function. This function is listed in
+Listing~\ref{lst:focus} and allows the programmer to fix the parametric lens to
+a value.
+
+\begin{lstlisting}[label={lst:focus},
+       caption={Parametric lens functions}]
+sdsFocus :: p (RWShared p r w) -> RWShared p` r w | iTask p
+\end{lstlisting}