diff -r 09ee9eb7a3d3 -r fd68c9c1b90b src/Pure/PIDE/resources.scala
--- a/src/Pure/PIDE/resources.scala	Tue Nov 17 16:54:49 2020 +0100
+++ b/src/Pure/PIDE/resources.scala	Tue Nov 17 22:05:59 2020 +0100
@@ -20,6 +20,31 @@
   resources =>
 
 
+  /* init session */
+
+  def init_session_yxml: String =
+  {
+    import XML.Encode._
+
+    YXML.string_of_body(
+      pair(list(pair(string, int)),
+      pair(list(pair(string, properties)),
+      pair(list(pair(string, string)),
+      pair(list(pair(string, string)),
+      pair(list(pair(string, list(string))),
+      pair(list(string),
+      pair(list(pair(string, string)), list(string))))))))(
+       (Symbol.codes,
+       (resources.sessions_structure.session_positions,
+       (resources.sessions_structure.dest_session_directories,
+       (resources.sessions_structure.session_chapters,
+       (resources.sessions_structure.bibtex_entries,
+       (resources.session_base.doc_names,
+       (resources.session_base.global_theories.toList,
+        resources.session_base.loaded_theories.keys)))))))))
+  }
+
+
   /* file formats */
 
   def make_theory_name(name: Document.Node.Name): Option[Document.Node.Name] =