Index: library/xotcl/library/xotcl2.tcl
===================================================================
diff -u -r764405083cfd6152d6956674e54f3a77cf7e1dcd -r65e384fc5b5fa044c63075f03756da88d316249f
--- library/xotcl/library/xotcl2.tcl	(.../xotcl2.tcl)	(revision 764405083cfd6152d6956674e54f3a77cf7e1dcd)
+++ library/xotcl/library/xotcl2.tcl	(.../xotcl2.tcl)	(revision 65e384fc5b5fa044c63075f03756da88d316249f)
@@ -79,25 +79,6 @@
   namespace import ::nsf::method::alias ::nsf::is ::nsf::relation
   interp alias {} ::xotcl::next {} ::nsf::xotclnext
 
-  #
-  # create ::xotcl::MetaSlot for better compatibility with XOTcl 1
-  #
-  ::nx::Class create ::xotcl::MetaSlot -superclass ::nx::MetaSlot {
-    :property parameter
-    :method init {} {
-      if {[info exists :parameter]} {my ::nsf::classes::xotcl::Class::parameter ${:parameter}}
-      next
-    }
-    # provide minimal compatibility
-    :public forward instproc %self public method
-    :public forward proc %self public class method
-  }
-
-  #
-  # Create ::xotcl::Attribute for compatibility
-  #
-  ::xotcl::MetaSlot create ::xotcl::Attribute -superclass ::nx::VariableSlot
-
   proc ::xotcl::self {{arg ""}} {
       switch $arg {
 	"" {uplevel ::nsf::self}
@@ -930,6 +911,42 @@
   proc myvar  {var}  {:requireNamespace; return [::xotcl::self]::$var}
 
   #
+  # create ::xotcl::MetaSlot for better compatibility with XOTcl 1
+  #
+  ::nx::Class create ::xotcl::MetaSlot -superclass ::nx::MetaSlot {
+    :property parameter
+    :method init {} {
+      if {[info exists :parameter]} {my ::nsf::classes::xotcl::Class::parameter ${:parameter}}
+      next
+    }
+    # provide minimal compatibility
+    :public forward instproc %self public method
+    :public forward proc %self public class method
+    #
+    # As NX/XOTcl hybrids, all slot kinds would not inherit the
+    # unknown behaviour of ::xotcl::Class. Therefore, we provide it
+    # explicitly to slots for backward compatibility ...
+    #
+    :public alias unknown ::nsf::classes::xotcl::Class::unknown
+  }
+
+  #
+  # Create ::xotcl::Attribute for compatibility
+  #
+  ::xotcl::MetaSlot create ::xotcl::Attribute -superclass ::nx::VariableSlot {
+    :property multivalued {
+      :public method assign {object property value} {
+	set mClass [expr {$value?"0..n":"1..1"}]
+	$object incremental $value
+	$object multiplicity $mClass
+      }
+      :public method get {object property} {
+	return [$object eval [list :isMultivalued]]
+      }
+    }
+  }
+
+  #
   # Provide a backward compatible version of ::xotcl::alias
   #
   ::nsf::proc ::xotcl::alias {
Index: library/xotcl/tests/slottest.xotcl
===================================================================
diff -u -r59e100d383b22ea1407f5e5c40e303f2c6bb9027 -r65e384fc5b5fa044c63075f03756da88d316249f
--- library/xotcl/tests/slottest.xotcl	(.../slottest.xotcl)	(revision 59e100d383b22ea1407f5e5c40e303f2c6bb9027)
+++ library/xotcl/tests/slottest.xotcl	(.../slottest.xotcl)	(revision 65e384fc5b5fa044c63075f03756da88d316249f)
@@ -568,12 +568,62 @@
 x move y
 ? {y a} 4
 
+::nx::Test case slots-compat
+#
+# Some tests covering the backward compatibility of NX/XOTcl2 hybrid
+# slots to the XOTcl1 slot API (as extracted from the XOTcl language
+# reference)
+#
+
+#
+# 1) old-style Attribute creation
+#
+  
+Class Window -slots {
+  Attribute scrollbar; # old style
+  Attribute create title; # new style
+}
+
+? {lsort [Window info slots]} "::Window::slot::scrollbar ::Window::slot::title"
+
+#
+# 2) Dropped/missing slot attributes: multivalued
+#
+
+Class Person -slots {
+  Attribute name
+  Attribute salary -default 0
+  Attribute projects -default {} -multivalued true
+}
+
+? {lsort [Person info slots]} "::Person::slot::name ::Person::slot::projects ::Person::slot::salary"
+
+? {Person::slot::name multivalued} 0
+? {Person::slot::salary multivalued} 0
+? {Person::slot::projects multivalued} 1
+
+Person p2 -name "John Doe"
+? {p2 name} "John Doe"
+? {p2 salary} "0"
+? {p2 projects} [list]
+
+Project compatPrj -name XOTclCompat
+p2 projects add ::compatPrj
+p2 projects add some-other-value
+
+? {lsort [p2 projects]} "::compatPrj some-other-value"
+p2 projects delete some-other-value
+? {lsort [p2 projects]} "::compatPrj"
+
+? {catch {p2 name add BOOM!}} 1
+? {p2 name} "John Doe"
+
 exit
 
-#puts [Person array get __defaults]
-#puts [Person serialize]
-puts [Serializer all]
-eval [Serializer all]
+  #puts [Person array get __defaults]
+  #puts [Person serialize]
+  puts [Serializer all]
+  eval [Serializer all]
 
 ? {p2 salary} 1009
 ? {catch {p2 append salary b}} 1
@@ -686,6 +736,10 @@
 puts stderr DONE-[p1 name]-[p1 age]
 
 p3 age 77
+
+
+
+
 exit
 
 puts [XoXML asXML]