--- a/AbstractHierarchicalItem.st	Wed Feb 08 18:41:24 2017 +0100
+++ b/AbstractHierarchicalItem.st	Fri Feb 10 11:22:12 2017 +0100
@@ -101,6 +101,16 @@
     ^ true
 ! !
 
+!AbstractHierarchicalItem class methodsFor:'queries'!
+
+isAbstract
+    "Return if this class is an abstract class.
+     True is returned here for myself only; false for subclasses.
+     Abstract subclasses must redefine this again."
+
+    ^ self == AbstractHierarchicalItem.
+! !
+
 !AbstractHierarchicalItem methodsFor:'accessing'!
 
 getChildren