Le mot clé `on grid` créera des flèches symétriques et `node distance=1 and 2` pour augmenter leur distance
distance.
\documentclass[tikz,10pt]{standalone}
\usetikzlibrary{positioning}
\tikzset{
abstract/.style={rectangle,draw=none,fill=yellow!30,on grid},
myarrow/.style={->,>=stealth}
}
\begin{document}
\begin{tikzpicture}[node distance=1 and 2]
\node (DS) [abstract]{lalala};
\node (FONDS) [abstract,below left=of DS]{lalalalalalalalalalalalalalalalala};
\node (LDS) [abstract,below right=of DS]{la};
\draw[myarrow,red] (FONDS.north) -- ++(0,0.3) -| ([xshift=-.2cm]DS.south);
\draw[myarrow,blue] (LDS.north) -- ++(0,0.3) -| ([xshift=.2cm]DS.south);
\end{tikzpicture}
\begin{tikzpicture}[node distance=1 and 3]
\node (DS) [abstract]{lalala};
\node (FONDS) [abstract,below left=of DS]{lalalalalalalalalalalalalalalalala};
\node (LDS) [abstract,below right=of DS]{la};
\draw[myarrow,red] (FONDS.north) -- ++(0,0.3) -| ([xshift=-.2cm]DS.south);
\draw[myarrow,blue] (LDS.north) -- ++(0,0.3) -| ([xshift=.2cm]DS.south);
\end{tikzpicture}
\end{document}
![alt text][1]
![alt text][2]
[1]: https://texnique.fr/osqa/upfiles/document_FNTvUcK.png
[2]: https://texnique.fr/osqa/upfiles/document_XYhkKZx.png
