diff --git a/research/try.cpp b/research/try.cpp
index 64085d3fd..fa95967bb 100644
--- a/research/try.cpp
+++ b/research/try.cpp
@@ -50,26 +50,89 @@ typedef unsigned int uint;
 #include "lib/symbol.hpp"
 #include "lib/diff/gen-node.hpp"
 #include "lib/time/timevalue.hpp"
+#include "lib/meta/generator.hpp"
+#include "lib/meta/typelist-manip.hpp"
 #include "lib/meta/tuple-helper.hpp"
 #include "lib/format-cout.hpp"
 #include "lib/format-util.hpp"
 
+#include <boost/noncopyable.hpp>
 #include <string>
 
 using lib::Literal;
+using lib::Variant;
+using lib::idi::EntryID;
 using lib::diff::Rec;
 using lib::diff::MakeRec;
 using lib::diff::GenNode;
+using lib::diff::DataValues;
 using lib::meta::Types;
 using lib::meta::Tuple;
 using lib::meta::IndexSeq;
 using lib::meta::BuildIndexSeq;
+using lib::meta::InstantiateChained;
+using lib::meta::Filter;
 using lib::time::TimeVar;
 using lib::time::Time;
 
 using std::string;
 using std::tuple;
 
+namespace error = lumiera::error;
+
+
+using DataCapPredicate = Variant<DataValues>::Predicate;
+
+
+template<typename TAR>
+class GenNodeAccessor
+  : boost::noncopyable
+  {
+    struct ConverterBase
+      : DataCapPredicate
+      {
+        char buffer[sizeof(TAR)];
+      };
+    
+    template<typename TY, class BA>
+    class Converter
+      : public BA
+      {
+        virtual bool
+        handle(TY const& srcElm)
+          {
+            new(&(BA::buffer)) TAR{srcElm};
+            return true;
+          };
+      };
+    
+    template<typename TY>
+    using can_Convert = std::is_constructible<TAR, TY const&>;
+    
+    using PossibleSourceTypes = typename Filter<DataValues::List, can_Convert>::List; 
+    
+    using ConversionBuffer = InstantiateChained< PossibleSourceTypes
+                                               , Converter
+                                               , ConverterBase
+                                               >;
+    
+    ConversionBuffer converter_;
+    
+  public:
+    GenNodeAccessor (GenNode const& node)
+      : converter_()
+      {
+        if (not node.data.accept (converter_))
+            throw error::Invalid ("Unable to build «" + util::typeStr<TAR>()
+                                 +"» element from " + string(node));
+      }
+    
+    operator TAR ()
+      {
+        return *reinterpret_cast<TAR*> (&converter_.buffer);
+      }
+  };
+
 
 template<class, size_t>
 struct Pick;
@@ -99,8 +162,7 @@ struct ElementMapper<Rec, Types<TYPES...>>
         
         operator TargetType<i> ()
           {
-            GenNode const& elm = values.child(i);
-            return elm.data.get<TargetType<i>>();
+            return GenNodeAccessor<TargetType<i>>(values.child(i));
           }
 
       };
@@ -164,17 +226,17 @@ int
 main (int, char**)
   {
     using NiceTypes = Types<string, int>;
-    using UgglyTypes = Types<Literal, string, short, long, float, TimeVar>;
+    using UgglyTypes = Types<EntryID<long>, string, short, long, float, TimeVar>;
     
-    using Uggs = Tuple<UgglyTypes>;
     
-//  Rec args = MakeRec().scope("lalü", "lala", 12, 34, 5.6, Time(7,8,9));
     Rec args = MakeRec().scope("lalü", 42);
+    Rec urgs = MakeRec().scope("lalü", "lala", 12, 34, 5.6, Time(7,8,9));
 
     cout << args <<endl;
+    cout << urgs <<endl;
     
-    auto uggs = buildTuple<NiceTypes> (args);
-    cout << uggs <<endl;
+    cout << buildTuple<NiceTypes> (args) <<endl;
+    cout << buildTuple<UgglyTypes> (urgs) <<endl;
     
     cout <<  "\n.gulp.\n";
     
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index bcbce4915..1ae8e82ab 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -736,15 +736,67 @@
 </node>
 <node CREATED="1453546436455" ID="ID_129001401" MODIFIED="1453546551564" TEXT="double-dispatch">
 <icon BUILTIN="idea"/>
-<node CREATED="1453546450317" ID="ID_1899026394" MODIFIED="1453546454089" TEXT="Variant-Visitor">
+<node CREATED="1453546450317" ID="ID_1899026394" MODIFIED="1453590519383" TEXT="Variant-Visitor">
+<icon BUILTIN="button_ok"/>
 <node CREATED="1453546485737" ID="ID_491338311" MODIFIED="1453546493300" TEXT="Gen-Node-Typen"/>
 <node CREATED="1453546493719" ID="ID_834270776" MODIFIED="1453546496947" TEXT="fest vorgegeben"/>
 </node>
-<node CREATED="1453546454484" ID="ID_1643300093" MODIFIED="1453546597358" TEXT="Trampolin">
-<icon BUILTIN="pencil"/>
+<node CREATED="1453546454484" ID="ID_1643300093" MODIFIED="1453590507167" TEXT="Trampolin">
+<icon BUILTIN="button_ok"/>
+</node>
+<node CREATED="1453546512277" ID="ID_968193365" MODIFIED="1453590559627" TEXT="Aufruf: generische Iteration">
+<icon BUILTIN="info"/>
+</node>
+<node CREATED="1453590522161" ID="ID_1369411965" MODIFIED="1453590545513" TEXT="Problem: narrowing conversions">
+<icon BUILTIN="messagebox_warning"/>
+<node BACKGROUND_COLOR="#fdfdcf" COLOR="#990000" CREATED="1453590566651" ID="ID_1367428687" MODIFIED="1453590610375" TEXT="TODO">
+<icon BUILTIN="flag"/>
+</node>
+<node CREATED="1453590585865" ID="ID_350595711" MODIFIED="1453590606670" TEXT="explizit gef&#xe4;hrliche ausschlie&#xdf;en">
+<icon BUILTIN="yes"/>
+</node>
+</node>
+<node CREATED="1453546467707" ID="ID_1543497504" MODIFIED="1453546472446" TEXT="Problem: template bloat">
+<node CREATED="1453590622236" ID="ID_1084684065" MODIFIED="1453590761460" TEXT="h&#xe4;lt sich in Grenzen">
+<icon BUILTIN="ksmiletris"/>
+<node CREATED="1453590828976" ID="ID_659078492" MODIFIED="1453590855465" TEXT="eine VTable pro Zieltyp"/>
+<node CREATED="1453590856220" ID="ID_376478329" MODIFIED="1453590879683">
+<richcontent TYPE="NODE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      eine virtuelle Funktion
+    </p>
+    <p>
+      pro m&#246;glichem Umwandlungs-Pfad
+    </p>
+  </body>
+</html>
+</richcontent>
+</node>
+</node>
+<node CREATED="1453590628419" ID="ID_1314031268" MODIFIED="1453590885601">
+<richcontent TYPE="NODE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      wir verwenden die Basis-VTable
+    </p>
+    <p>
+      und layern nur die tats&#228;chlich m&#246;glichen Umwandlungen dr&#252;ber
+    </p>
+  </body>
+</html>
+</richcontent>
+<icon BUILTIN="info"/>
+</node>
+<node CREATED="1453590667630" ID="ID_792450888" MODIFIED="1453590699782" TEXT="&#xfc;berpr&#xfc;ft: mit -O3 und strip bleibt erstaunlich wenig &#xfc;brig"/>
+<node CREATED="1453590741428" ID="ID_1733557933" MODIFIED="1453590749327" TEXT="1.6MiB -&gt; 100k"/>
 </node>
-<node CREATED="1453546467707" ID="ID_1543497504" MODIFIED="1453546472446" TEXT="Problem: template bloat"/>
-<node CREATED="1453546512277" ID="ID_968193365" MODIFIED="1453546526943" TEXT="Aufruf: generische Iteration"/>
 </node>
 </node>
 </node>