--- a/Layout.st	Fri Feb 10 11:19:03 2017 +0100
+++ b/Layout.st	Fri Feb 10 11:19:32 2017 +0100
@@ -73,6 +73,16 @@
     "Modified: 27.4.1996 / 14:47:08 / cg"
 ! !
 
+!Layout 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 == Layout.
+! !
+
 !Layout methodsFor:'converting'!
 
 asLayout