\begin{tikzpicture}[scale=1.0]
  \small
  
  \draw(0pt,0pt) -- (40pt,30pt);
  \draw(40pt,-10pt) -- (40pt,30pt);
  \draw(80pt,0pt) -- (40pt,30pt);
  \draw(40pt,30pt) -- (40pt,42pt);

  \draw[fill=white] (0pt,0pt) circle (8pt);
  \draw[fill=white] (40pt,-10pt) circle (8pt);  
  \draw[fill=white]  (80pt,0pt) circle (8pt);

  \draw[fill=darkgray] (40pt,30pt) circle (8pt);

  \draw (48pt,48pt) node[anchor=west]{Document};

  \draw (48pt,30pt) node[anchor=west]{Service provider};

  \draw[fill=green] (34pt, 42pt) rectangle (46pt,54pt);
  
\end{tikzpicture}