diff -r 9e86c1ca6e51 -r 99eefb83a35d src/Pure/General/markup.scala
--- a/src/Pure/General/markup.scala	Wed Dec 30 22:29:37 2009 +0100
+++ b/src/Pure/General/markup.scala	Wed Dec 30 22:56:46 2009 +0100
@@ -159,7 +159,6 @@
   /* messages */
 
   val PID = "pid"
-  val SESSION = "session"
 
   val MESSAGE = "message"
   val CLASS = "class"