diff --git a/src/proc/control/command-argument-holder.hpp b/src/proc/control/command-argument-holder.hpp
index e196e4698..11480695c 100644
--- a/src/proc/control/command-argument-holder.hpp
+++ b/src/proc/control/command-argument-holder.hpp
@@ -45,6 +45,7 @@
 
 //#include "pre.hpp"
 //#include "lib/error.hpp"
+#include "proc/control/argument-tuple-accept.hpp"
 #include "proc/control/command-closure.hpp"
 #include "proc/control/memento-tie.hpp"
 
@@ -104,14 +105,17 @@ namespace control {
    * actually allocating storage to hold the command arguments
    * and the undo state (memento) for Proc-Layer commands.
    * Both the contained components within ArgumentHolder 
-   * can be in \em empty state; there is no distinct
+   * can be in \em empty state; there are no distinct
    * lifecycle limitations. ArgumentHolder is part
    * of Proc-Layer command's implementation
    * and should not be used standalone. 
    */
   template<typename SIG, typename MEM>
   class ArgumentHolder
-    : public CmdClosure
+    : public ArgumentTupleAccept< SIG                      // to derive the desired bind(..) signature
+                                , ArgumentHolder<SIG,MEM>  // target class providing the implementation
+                                , CmdClosure               // base class to inherit from
+                                >    
     {
       Closure<SIG> arguments_;
       MementoTie<SIG,MEM> memento_;
@@ -141,8 +145,8 @@ namespace control {
       virtual operator string()  const
         {
           return "Command-State{ arguments="
-               + arguments_? arguments_ : "unbound"
-               + memento_  ? ", <memento> }" : "<no undo> }"
+               + (arguments_? string(arguments_) : "unbound")
+               + (memento_  ?    ", <memento> }" : "<no undo> }")
                ;
         }
       
@@ -159,14 +163,14 @@ namespace control {
         { }
       
       /** has undo state capturing been invoked? */
-      bool canUndo () { return bool(memento_); }
-      bool empty ()   { return !arguments_; }
+      bool canUndo () const { return bool(memento_); }
+      bool empty ()   const { return !arguments_; }
       
       
       /** store a new argument tuple within this ArgumentHolder,
        *  discarding and previously stored arguments */
       void
-      bind (ArgTuple argTup)
+      bindArg (ArgTuple argTup)
         {
           this->arguments_ = Closure<SIG> (argTup);
         }
@@ -185,6 +189,15 @@ namespace control {
           return this->memento_ = MementoTie<SIG,MEM> (undoFunc,captureFunc);
         }
       
+      
+      /** direct "backdoor" access to stored memento value.
+       *  @note you might access a placeholder when called prior to \c tie(..) */
+      MEM&
+      memento ()
+        {
+          return memento_.getState();
+        }
+      
     };
   
     
diff --git a/src/proc/control/command-closure.hpp b/src/proc/control/command-closure.hpp
index 34498fe18..71dbe7384 100644
--- a/src/proc/control/command-closure.hpp
+++ b/src/proc/control/command-closure.hpp
@@ -97,7 +97,7 @@ namespace control {
       
       virtual operator string() const =0;
       
-      virtual bool isValid ()   const { return true; }
+      virtual bool isValid ()   const =0;
       
       virtual CmdFunctor bindArguments (CmdFunctor&) =0;
     };
@@ -212,6 +212,9 @@ namespace control {
           else
             return dumped+")";
         }
+      
+      
+      bool isValid ()  const { return true; }
     };
     
     
diff --git a/tests/components/proc/control/command-argument-test.cpp b/tests/components/proc/control/command-argument-test.cpp
index 3ff10cc23..e796d9646 100644
--- a/tests/components/proc/control/command-argument-test.cpp
+++ b/tests/components/proc/control/command-argument-test.cpp
@@ -51,7 +51,8 @@
 //using std::tr1::placeholders::_2;
 //using std::tr1::function;
 using util::isnil;
-using util::and_all;
+//using util::and_all;
+using util::for_each;
 using boost::format;
 using lumiera::Time;
 //using util::contains;
@@ -178,46 +179,60 @@ namespace test    {
       virtual void
       run (Arg) 
         {
-#if false ////////////////////////////////////////////////////////////////////////////TODO.....          
           ArgTuples testTuples;
           Tracker<Time>::instanceCnt = 0;
           Tracker<string>::instanceCnt = 0;
           
-          createArgTuples (testTuples);
-          checkArgumentComparison ();
-          serialiseArgTuples (testTuples);
+          createTuples (testTuples);
+//        checkArgumentComparison ();
+//        serialiseArgTuples (testTuples);
           
-          simulateCmdLifecycle();
+//        simulateCmdLifecycle();
           
           ASSERT (0 == Tracker<Time>::instanceCnt);
           ASSERT (0 == Tracker<string>::instanceCnt);
         }
       
+      typedef struct{ int i[5]; } Sint5;
+          
       
       /** @test create various argument tuples and re-access their contents */
       void
       createTuples (ArgTuples& tup)
         {
-          tup.manage (new ArgumentHolder<void()>);
-          tup.manage (new ArgumentHolder<void(int)>);
-          tup.manage (new ArgumentHolder<void(int,Time)>);
-          tup.manage (new ArgumentHolder<void(int,Time), Time>);
-          tup.manage (new ArgumentHolder<void(int,Time), int[5]>);
+          typedef ArgumentHolder<void(),         bool>  A1;
+          typedef ArgumentHolder<void(int),      void*> A2;
+          typedef ArgumentHolder<void(int,Time), int>   A3;
+          typedef ArgumentHolder<void(int,Time), Time>  A4;
+          typedef ArgumentHolder<void(int,Time), Sint5> A5;
           
-          ASSERT (and_all (tup, isnil));
+          A1* arg1 = new A1(); tup.manage (arg1);
+          A2* arg2 = new A2(); tup.manage (arg2);
+          A3* arg3 = new A3(); tup.manage (arg3);
+          A4* arg4 = new A4(); tup.manage (arg4);
+          A5* arg5 = new A5(); tup.manage (arg5);
+          
+          ASSERT (isnil (*arg1));
+          ASSERT (isnil (*arg2));
+          ASSERT (isnil (*arg3));
+          ASSERT (isnil (*arg4));
+          ASSERT (isnil (*arg5));
           
           for_each (tup, showIt);
           
-          tup[1].bind (rand() % 20);
-          tup[2].bind (rand() % 20, randTime());
-          tup[3].bind (rand() % 20, randTime());
-          tup[4].bind (rand() % 20, randTime());
+          arg2->bind (rand() % 20);
+          arg3->bind (rand() % 20, randTime());
+          arg4->bind (rand() % 20, randTime());
+          arg5->bind (rand() % 20, randTime());
           
-          tup[1].memento() = 42;
-          tup[4].memento()[3] = 513;
+          arg3->memento() = 42;
+          arg5->memento().i[3] = 513;
+          
+          for_each (tup, showIt);
         }
       
       
+#if false ////////////////////////////////////////////////////////////////////////////TODO.....          
       /** @test serialise and de-serialise each tuple and check validity
        *  @todo unimplemented, waiting on Serialiser
        */
@@ -319,8 +334,8 @@ namespace test    {
           
           bound_undoFun();
           cout << protocol.str() << endl;
-#endif ////////////////////////////////////////////////////////////////////////////TODO.....          
         }
+#endif ////////////////////////////////////////////////////////////////////////////TODO.....          
     };
   
   
diff --git a/tests/lib/opaque-unchecked-buffer-test.cpp b/tests/lib/opaque-unchecked-buffer-test.cpp
new file mode 100644
index 000000000..b7be45f8a
--- /dev/null
+++ b/tests/lib/opaque-unchecked-buffer-test.cpp
@@ -0,0 +1,302 @@
+/*
+  OpaqueHolder(Test)  -  check the inline type erasure helper
+ 
+  Copyright (C)         Lumiera.org
+    2009,               Hermann Vosseler <Ichthyostega@web.de>
+ 
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License as
+  published by the Free Software Foundation; either version 2 of the
+  License, or (at your option) any later version.
+ 
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+ 
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ 
+* *****************************************************/
+
+
+
+#include "lib/test/run.hpp"
+#include "lib/test/test-helper.hpp"
+#include "lib/util.hpp"
+
+#include "lib/opaque-holder.hpp"
+#include "lib/bool-checkable.hpp"
+
+#include <iostream>
+#include <vector>
+
+
+namespace lib {
+namespace test{
+  
+  using ::Test;
+  using util::isnil;
+  using util::for_each;
+  using util::isSameObject;
+  using lumiera::error::LUMIERA_ERROR_INVALID;
+  using lumiera::error::LUMIERA_ERROR_ASSERTION;
+  
+  using std::vector;
+  using std::cout;
+  using std::endl;
+  
+  namespace { // test dummy hierarchy
+             //  Note: common storage but no vtable 
+    
+    long _checksum = 0;
+    uint _create_count = 0;
+    
+    
+    struct Base   
+      {
+        uint id_;
+        
+        Base(uint i=0)      : id_(i)     { _checksum +=id_; ++_create_count; }
+        Base(Base const& o) : id_(o.id_) { _checksum +=id_; ++_create_count; }
+        
+        uint getIt() { return id_; }
+      };
+    
+    
+    template<uint ii>
+    struct DD : Base
+      {
+        DD() : Base(ii)       { }
+       ~DD() { _checksum -= ii; }  // doing the decrement here
+      };                          //  verifies the correct dtor is called
+    
+    
+    struct Special
+      : DD<7>
+      , BoolCheckable<Special>
+      {
+        ulong myVal_;
+        
+        Special (uint val)
+          : myVal_(val)
+          { }
+        
+        bool
+        isValid ()  const ///< custom boolean "validity" check
+          {
+            return myVal_ % 2;
+          }
+      };
+    
+    
+    /** maximum additional storage maybe wasted
+     *  due to alignment of the contained object
+     *  within OpaqueHolder's buffer
+     */
+    const size_t _ALIGN_ = sizeof(size_t);
+    
+  }
+  
+  typedef OpaqueHolder<Base> Opaque;
+  typedef vector<Opaque> TestList;
+  
+  
+  
+  /**********************************************************************************
+   *  @test use the OpaqueHolder inline buffer to handle objects of a family of types
+   *        through a common interface, without being forced to use heap storage
+   *        or a custom allocator.
+   *
+   *  @todo this test doesn't cover automatic conversions and conversions using RTTI
+   *        from the target objects, while \code OpaqueHolder.template get() \endcode
+   *        would allow for such conversions. This is similar to Ticket #141, and
+   *        actually based on the same code as variant.hpp (access-casted.hpp)
+   */
+  class OpaqueHolder_test : public Test
+    {
+      
+      virtual void
+      run (Arg)
+        {
+          _checksum = 0;
+          _create_count = 0;
+          {
+            TestList objs = createDummies ();
+            for_each (objs, reAccess);
+            checkHandling (objs);
+            checkSpecialSubclass ();
+          }
+          ASSERT (0 == _checksum); // all dead
+        }
+      
+      
+      TestList
+      createDummies ()
+        {
+          TestList list;
+          list.push_back (DD<1>());
+          list.push_back (DD<3>());
+          list.push_back (DD<5>());
+          list.push_back (DD<7>());
+          return list;
+        } //note: copy
+      
+      
+      static void
+      reAccess (Opaque& elm)
+        {
+          cout << elm->getIt() << endl;
+        }
+      
+      
+      /** @test cover the basic situations of object handling,
+       *        especially copy operations and re-assignments
+       */
+      void
+      checkHandling (TestList& objs)
+        {
+          Opaque oo;
+          ASSERT (!oo);
+          ASSERT (isnil(oo));
+          
+          oo = objs[1];
+          ASSERT (oo);
+          ASSERT (!isnil(oo));
+          
+          typedef DD<3> D3;
+          typedef DD<5> D5;
+          D3 d3 (oo.get<D3>() );
+          ASSERT (3 == oo->getIt());    // re-access through Base interface
+          ASSERT (!isSameObject (d3, *oo));
+          VERIFY_ERROR (WRONG_TYPE, oo.get<D5>() );
+          
+          // direct assignment of target into Buffer
+          oo = D5();
+          ASSERT (oo);
+          ASSERT (5 == oo->getIt());
+          VERIFY_ERROR (WRONG_TYPE, oo.get<D3>() );
+          
+          // can get a direct reference to contained object
+          D5 &rd5 (oo.get<D5>()); 
+          ASSERT (isSameObject (rd5, *oo));
+          
+          ASSERT (!isnil(oo));
+          oo = objs[3];     // copy construction also works on non-empty object
+          ASSERT (7 == oo->getIt());
+          
+          // WARNING: direct ref has been messed up through the backdoor!
+          ASSERT (7 == rd5.getIt());
+          ASSERT (isSameObject (rd5, *oo));
+          
+          uint cnt_before = _create_count;
+          
+          oo.clear();
+          ASSERT (!oo);
+          oo = D5();        // direct assignment also works on empty object
+          ASSERT (oo);
+          ASSERT (5 == oo->getIt());
+          ASSERT (_create_count == 2 + cnt_before);
+          // one within buff and one for the anonymous temporary D5()
+          
+          
+          // verify that self-assignment is properly detected...
+          cnt_before = _create_count;
+          oo = oo;
+          ASSERT (oo);
+          ASSERT (_create_count == cnt_before);
+          oo = oo.get<D5>();
+          ASSERT (_create_count == cnt_before);
+          oo = *oo;
+          ASSERT (_create_count == cnt_before);
+          ASSERT (oo);
+          
+          oo.clear();
+          ASSERT (!oo);
+          ASSERT (isnil(oo));
+          VERIFY_ERROR (INVALID, oo.get<D5>() );
+#if false ////////////////////////////////////////////////////////TODO: restore throwing ASSERT
+          VERIFY_ERROR (ASSERTION, oo->getIt() );
+#endif////////////////////////////////////////////////////////////
+          // can't access empty holder...
+          
+          Opaque o1 (oo);
+          ASSERT (!o1);
+          
+          Opaque o2 (d3);
+          ASSERT (!isSameObject (d3, *o2));
+          ASSERT (3 == o2->getIt());
+          
+          ASSERT (sizeof(Opaque) <= sizeof(Base) + sizeof(void*) + _ALIGN_);
+        }
+      
+      
+      /** @test OpaqueHolder with additional storage for subclass.
+       *        When a subclass requires more storage than the base class or
+       *        Interface, we need to create a custom OpaqueHolder, specifying the
+       *        actually necessary storage. Such a custom OpaqueHolder behaves exactly
+       *        like the standard variant, but there is protection against accidentally
+       *        using a standard variant to hold an instance of the larger subclass.
+       *        
+       *  @test Moreover, if the concrete class has a custom operator bool(), it
+       *        will be invoked automatically from OpaqueHolder's operator bool()
+       * 
+       */ 
+      void
+      checkSpecialSubclass ()
+        {
+          typedef OpaqueHolder<Base, sizeof(Special)> SpecialOpaque;
+          
+          cout << showSizeof<Base>() << endl;
+          cout << showSizeof<Special>() << endl;
+          cout << showSizeof<Opaque>() << endl;
+          cout << showSizeof<SpecialOpaque>() << endl;
+          
+          ASSERT (sizeof(Special) > sizeof(Base));
+          ASSERT (sizeof(SpecialOpaque) > sizeof(Opaque));
+          ASSERT (sizeof(SpecialOpaque) <= sizeof(Special) + sizeof(void*) + _ALIGN_);
+          
+          Special s1 (6);
+          Special s2 (3);
+          ASSERT (!s1);               // even value
+          ASSERT (s2);                // odd value
+          ASSERT (7 == s1.getIt());   // indeed subclass of DD<7>
+          ASSERT (7 == s2.getIt());
+          
+          SpecialOpaque ospe0;
+          SpecialOpaque ospe1 (s1);
+          SpecialOpaque ospe2 (s2);
+          
+          ASSERT (!ospe0);            // note: bool test (isValid)
+          ASSERT (!ospe1);            // also forwarded to contained object (myVal_==6 is even)
+          ASSERT ( ospe2);
+          ASSERT ( isnil(ospe0));     // while isnil just checks the empty state
+          ASSERT (!isnil(ospe1));
+          ASSERT (!isnil(ospe2));
+          
+          ASSERT (7 == ospe1->getIt());
+          ASSERT (6 == ospe1.get<Special>().myVal_);
+          ASSERT (3 == ospe2.get<Special>().myVal_);
+          
+          ospe1 = DD<5>();            // but can be reassigned like any normal Opaque
+          ASSERT (ospe1);
+          ASSERT (5 == ospe1->getIt());
+          VERIFY_ERROR (WRONG_TYPE, ospe1.get<Special>() );
+          
+          Opaque normal = DD<5>();
+          ASSERT (normal);
+          ASSERT (5 == normal->getIt());
+#if false ////////////////////////////////////////////////////////TODO: restore throwing ASSERT
+          // Assertion protects against SEGV
+          VERIFY_ERROR (ASSERTION, normal = s1 );
+#endif////////////////////////////////////////////////////////////
+        }
+    };
+  
+  
+  LAUNCHER (OpaqueHolder_test, "unit common");
+  
+  
+}} // namespace lib::test
+