\section{The Backend Design}

\subsection{The Template}
OPimAccessBackend is a template interface of the backend. 
It consists out of pure virtual functions for
load, reload, save and clear, add, remove and replace.
Special inheritances from OPimAccessBackend for todo, calendar-event and conatact are available to 
define the backend Type with additional functionality and some implementations for special queries.

\subsection{Caching}
You may implement caching by implementing a specific find function. It is filling the cache 
(located in the frontend) as read-ahed or read-behing, by giving a read direction. 
\comment{ Das versteht an dieser Stelle keiner: First you need to give the Frontend
a hint on how many items you want to cache and then you can call
cache to cache items.
read-ahead returns the number of records to read behind/ahead.}
Caching is used automatically, if this function is implemented.
