diff --git a/docs/design/design-3.html b/docs/design/design-3.html
index bc57b17f1..e1b07d304 100644
--- a/docs/design/design-3.html
+++ b/docs/design/design-3.html
@@ -280,7 +280,7 @@
     their relationships</p>
 
     <center>
-      <image alt="to be added">
+      <img src="simple-model.png" width=453 height=378>
     </center>
 
     <p>Note that this picture will be updated at the end of the next
diff --git a/docs/design/simple-model.png b/docs/design/simple-model.png
new file mode 100644
index 000000000..25434044e
Binary files /dev/null and b/docs/design/simple-model.png differ