\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 \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
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 which
-starts a new task according to specified predicates on the \CI{TaskValue}.
-Type signatures of the basic combinators are shown in
+starts a new \gls{Task} according to specified predicates on the
+\CI{TaskValue}. Type signatures of the basic combinators are shown in
Listing~\ref{lst:combinators}.
\begin{itemize}
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.
+memory, other \glspl{SDS} 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.
+\glspl{SDS} 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 \glspl{Task} 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}]
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
+\gls{SDS}, and have \glspl{Task} only look at parts of the big \gls{SDS}. 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
+contains a map that is accessible through a \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 specific value.
+functions are the \CI{sdsFocus} and the \CI{sdsLens} function. These functions
+are listed in Listing~\ref{lst:focus}. \CI{sdsFocus} allows the programmer to
+fix a parametric lens value. \CI{sdsLens} is a kind of \CI{mapReadWrite}
+including access to the parametric lens value. This allows the creation of
+for example \glspl{SDS} that only read and write to parts of the original
+\gls{SDS}.
\begin{lstlisting}[label={lst:focus},
caption={Parametric lens functions}]
sdsFocus :: p (RWShared p r w) -> RWShared p` r w | iTask p
+
+:: SDSNotifyPred p :== p -> Bool
+
+:: SDSLensRead p r rs = SDSRead (p -> rs -> MaybeError TaskException r)
+ | SDSReadConst (p -> r)
+:: SDSLensWrite p w rs ws = SDSWrite (p -> rs -> w -> MaybeError TaskException (Maybe ws))
+ | SDSWriteConst (p -> w -> MaybeError TaskException (Maybe ws))
+:: SDSLensNotify p w rs = SDSNotify (p -> rs -> w -> SDSNotifyPred p)
+ | SDSNotifyConst (p -> w -> SDSNotifyPred p)
+
+sdsLens :: String (p -> ps) (SDSLensRead p r rs) (SDSLensWrite p w rs ws) (SDSLensNotify p w rs)
+ (RWShared ps rs ws) -> RWShared p r w | iTask ps
\end{lstlisting}
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