src/Pure/System/isabelle_process.scala

     def is_exit = kind == Markup.EXIT
     def is_stdout = kind == Markup.STDOUT
     def is_system = kind == Markup.SYSTEM
     def is_status = kind == Markup.STATUS
     def is_report = kind == Markup.REPORT
-    def is_ready = is_status && {
-      body match {
-        case List(XML.Elem(Markup(Markup.READY, _), _)) => true
-        case _ => false
-      }}
+    def is_ready = Isar_Document.is_ready(message)
+    def is_syslog = is_init || is_exit || is_system || is_ready
 
     override def toString: String =
     {
       val res =
         if (is_status || is_report) message.body.map(_.toString).mkString