diff -r d7fa4daf7ba7 -r 88dfbc382a3d src/Pure/PIDE/markup.scala
--- a/src/Pure/PIDE/markup.scala	Fri Apr 03 11:47:08 2020 +0200
+++ b/src/Pure/PIDE/markup.scala	Fri Apr 03 12:45:14 2020 +0200
@@ -549,79 +549,65 @@
   /* protocol message functions */
 
   val FUNCTION = "function"
-  val Function = new Properties.String(FUNCTION)
 
-  val COMMAND_TIMING: Properties.Entry = (FUNCTION, "command_timing")
-  val THEORY_TIMING: Properties.Entry = (FUNCTION, "theory_timing")
+  class Function(val name: String)
+  {
+    val PROPERTY: Properties.Entry = (FUNCTION, name)
+  }
 
-  val Commands_Accepted: Properties.T = List((FUNCTION, "commands_accepted"))
-  val Assign_Update: Properties.T = List((FUNCTION, "assign_update"))
-  val Removed_Versions: Properties.T = List((FUNCTION, "removed_versions"))
-
-  object Protocol_Handler
+  class Properties_Function(name: String) extends Function(name)
   {
-    def unapply(props: Properties.T): Option[(String)] =
+    def unapply(props: Properties.T): Option[Properties.T] =
       props match {
-        case List((FUNCTION, "protocol_handler"), (NAME, name)) => Some(name)
+        case PROPERTY :: args => Some(args)
         case _ => None
       }
   }
 
-  val INVOKE_SCALA = "invoke_scala"
-  object Invoke_Scala
+  class Name_Function(name: String) extends Function(name)
   {
-    def unapply(props: Properties.T): Option[(String, String)] =
+    def unapply(props: Properties.T): Option[(String)] =
       props match {
-        case List((FUNCTION, INVOKE_SCALA), (NAME, name), (ID, id)) => Some((name, id))
+        case List(PROPERTY, (NAME, a)) => Some(a)
         case _ => None
       }
   }
 
-  val CANCEL_SCALA = "cancel_scala"
-  object Cancel_Scala
+  object Command_Timing extends Properties_Function("command_timing")
+  object Theory_Timing extends Properties_Function("theory_timing")
+  object ML_Statistics extends Properties_Function("ML_statistics")
+  object Task_Statistics extends Properties_Function("task_statistics")
+
+  object Loading_Theory extends Name_Function("loading_theory")
+  object Build_Session_Finished extends Function("build_session_finished")
+
+  object Protocol_Handler extends Name_Function("protocol_handler")
+
+  object Commands_Accepted extends Function("commands_accepted")
+  object Assign_Update extends Function("assign_update")
+  object Removed_Versions extends Function("removed_versions")
+
+  object Invoke_Scala extends Function("invoke_scala")
   {
-    def unapply(props: Properties.T): Option[String] =
+    def unapply(props: Properties.T): Option[(String, String)] =
       props match {
-        case List((FUNCTION, CANCEL_SCALA), (ID, id)) => Some(id)
-        case _ => None
-      }
-  }
-
-  object ML_Statistics
-  {
-    def unapply(props: Properties.T): Option[Properties.T] =
-      props match {
-        case (FUNCTION, "ML_statistics") :: props => Some(props)
+        case List(PROPERTY, (NAME, name), (ID, id)) => Some((name, id))
         case _ => None
       }
   }
 
-  object Task_Statistics
+  object Cancel_Scala extends Function("cancel_scala")
   {
-    def unapply(props: Properties.T): Option[Properties.T] =
+    def unapply(props: Properties.T): Option[String] =
       props match {
-        case (FUNCTION, "task_statistics") :: props => Some(props)
+        case List(PROPERTY, (ID, id)) => Some(id)
         case _ => None
       }
   }
 
-  val LOADING_THEORY = "loading_theory"
-  object Loading_Theory
-  {
-    def unapply(props: Properties.T): Option[String] =
-      props match {
-        case List((FUNCTION, LOADING_THEORY), (NAME, name)) => Some(name)
-        case _ => None
-      }
-  }
-
-  val BUILD_SESSION_FINISHED = "build_session_finished"
-  val Build_Session_Finished: Properties.T = List((FUNCTION, BUILD_SESSION_FINISHED))
-
   val PRINT_OPERATIONS = "print_operations"
 
 
-
   /* export */
 
   val EXPORT = "export"