diff --git a/NOTES.thy b/NOTES.thy
index a689bd3c..f45aea38 100644
--- a/NOTES.thy
+++ b/NOTES.thy
@@ -80,6 +80,17 @@ text \<open>
 
 section \<open>Document preparation in Isabelle/ML\<close>
 
+subsection \<open>Session presentation hook\<close>
+
+text \<open>
+  \<^ML>\<open>Build.add_hook\<close> allows to install a global session presentation
+  hook. It is used e.g. in Isabelle/Mirabelle to analyze all loaded
+  theories via Sledgehammer and other tools. Isabelle/DOF could use it to
+  "wrap-up" the whole session, to check if all document constraints hold
+  (cf. "monitors").
+\<close>
+
+
 subsection \<open>Theory presentation hook\<close>
 
 text \<open>
@@ -129,6 +140,15 @@ ML \<open>
 \<close>
 
 
+subsection \<open>Document content\<close>
+
+text \<open>
+  XML is now used uniformly (sometimes as inlined YXML). The meaning of
+  markup elements and properties is defined in
+  \<^scala_type>\<open>isabelle.Latex.Output\<close> (or user-defined subclasses).
+\<close>
+
+
 section \<open>Isabelle/Scala services\<close>
 
 subsection \<open>Isabelle/DOF/Scala module\<close>