On the picture below (generated with TikZ library), I would like to put AA above its arrow, and BB below its arrow:
Here is my code so far:
\begin{figure}
\centering
\begin{tikzpicture}[thick, node distance=9em and 15em, every node/.style={align=center}]
% Nodes
\node[block, drop shadow=black, fill=lightgray] (space) {Search Space};
\node[block, drop shadow=black, fill=lightgray, right of=space, xshift=1cm] (strategy) {Search Strategy};
\node[block, drop shadow=black, fill=lightgray, right of=strategy,xshift=3cm] (performance){Performance \\Estimation Strategy};
% Arrows
\path[-latex] (space) edge node[fill=white, anchor=center, inner sep=2pt] {a} (strategy);
\path[-latex] (strategy) edge[bend left=0.5cm] node[fill=white, anchor=center, yshift=-0.1cm] {AA} (performance);
\path[-latex] (performance) edge[bend left=0.5cm] node[fill=white, anchor=center, yshift=0.1cm] {BB} (strategy);
\end{tikzpicture}
\caption{Graph-based structure of the behaviours}
\label{fig:nas-def}
\end{figure}
I could not find anywhere how to do this, any idea ?