diff --git a/src/proc/asset/entry-id.hpp b/src/proc/asset/entry-id.hpp
index 6a6bbcd9f..632561e77 100644
--- a/src/proc/asset/entry-id.hpp
+++ b/src/proc/asset/entry-id.hpp
@@ -87,7 +87,7 @@ namespace asset {
       boost::hash_combine(seed, sym);
       lumiera_uid tmpLUID;
       lumiera_uid_set_ptr (&tmpLUID, reinterpret_cast<void*> (&seed));
-      return reinterpret_cast<LuidH> (tmpLUID);
+      return reinterpret_cast<LuidH&> (tmpLUID);
     }
   }
   
@@ -110,9 +110,9 @@ namespace asset {
       
     public:
       explicit
-      BareEntryID (string const& symbolID, HashVal seed =0)        /////////////TODO couldn't this be protected?
+      BareEntryID (string const& symbolID, idi::HashVal seed =0)        /////////////TODO couldn't this be protected?
         : symbol_(util::sanitise(symbolID))
-        , hash_(buildHash (symbol_, seed))
+        , hash_(idi::buildHash (symbol_, seed))
         { }
       
       /* default copy- and assignable */
@@ -138,7 +138,7 @@ namespace asset {
       
       /** using BareEntryID derived objects as keys within tr1::unordered_map */
       struct UseEmbeddedHash
-        : public std::unary_function<BA, size_t>
+        : public std::unary_function<BareEntryID, size_t>
         {
           size_t operator() (BareEntryID const& obj)  const { return obj.getHash(); }
         };
@@ -190,7 +190,7 @@ namespace asset {
       getIdent()  const
         {
           Category cat (STRUCT, idi::StructTraits<TY>::catFolder);
-          return Asset::Ident (name, cat);           
+          return Asset::Ident (this->getSym(), cat);           
         }
       
       static idi::HashVal
@@ -225,7 +225,7 @@ namespace asset {
       
       operator string ()  const
         {
-          return "ID<"+idi::StructTraits<TY>::idSymbol+">-"+getSym();
+          return "ID<"+idi::StructTraits<TY>::idSymbol+">-"+EntryID::getSym();
         }
   
       friend ostream& operator<<   (ostream& os, EntryID const& id) { return os << string(id); }
diff --git a/src/proc/asset/struct-factory-impl.hpp b/src/proc/asset/struct-factory-impl.hpp
index 6cf87e215..0fe969261 100644
--- a/src/proc/asset/struct-factory-impl.hpp
+++ b/src/proc/asset/struct-factory-impl.hpp
@@ -37,7 +37,8 @@
 
 
 #include "proc/mobject/session.hpp"
-#include "proc/mobject/mobject.hpp"
+#include "proc/mobject/session/binding.hpp"
+#include "proc/mobject/session/mobjectfactory.hpp"
 #include "common/configrules.hpp"
 #include "proc/asset/timeline.hpp"
 #include "proc/asset/sequence.hpp"
diff --git a/src/proc/mobject/session/binding.cpp b/src/proc/mobject/session/binding.cpp
index 8aa2a9bc7..955d94149 100644
--- a/src/proc/mobject/session/binding.cpp
+++ b/src/proc/mobject/session/binding.cpp
@@ -28,7 +28,7 @@ namespace mobject {
 namespace session {
   
   /** */
-  Binding::Binding (PSequence& sequence_to_bind)
+  Binding::Binding (PSequence const& sequence_to_bind)
     : boundSequence_(sequence_to_bind)
     {
       throwIfInvalid();
diff --git a/src/proc/mobject/session/binding.hpp b/src/proc/mobject/session/binding.hpp
index 0f588eb91..135482e57 100644
--- a/src/proc/mobject/session/binding.hpp
+++ b/src/proc/mobject/session/binding.hpp
@@ -28,12 +28,17 @@
 #include "proc/mobject/builder/buildertool.hpp"
 
 
-namespace asset { class Sequence; }
+namespace asset { 
+  class Sequence;
+  
+  typedef lumiera::P<Sequence> PSequence;
+
+}
 
 namespace mobject {
 namespace session {
   
-    typedef lumiera::P<asset::Sequence> PSequence;
+    using asset::PSequence;
     
     /**
      * Explicit link to bind a Sequence (container) to be used within the Session,
@@ -48,7 +53,7 @@ namespace session {
         bool isValid()  const;
         
       public:
-        Binding (PSequence& sequence_to_bind);
+        Binding (PSequence const& sequence_to_bind);
           
         DEFINE_PROCESSABLE_BY (builder::BuilderTool);
 
diff --git a/src/proc/mobject/session/mobjectfactory.cpp b/src/proc/mobject/session/mobjectfactory.cpp
index fc1a2ccbf..d08bc7e3a 100644
--- a/src/proc/mobject/session/mobjectfactory.cpp
+++ b/src/proc/mobject/session/mobjectfactory.cpp
@@ -99,7 +99,7 @@ namespace session {
   
   /** */ 
   Placement<Binding>
-  MObjectFactory::operator() (PSequence& sequence_to_bind)
+  MObjectFactory::operator() (PSequence const& sequence_to_bind)
   {
     TODO ("any additional liabilities when creating a binding?");
     return Placement<Binding> (*new Binding(sequence_to_bind), &deleterFunc);
diff --git a/src/proc/mobject/session/mobjectfactory.hpp b/src/proc/mobject/session/mobjectfactory.hpp
index 6b9ccfca5..972bc6628 100644
--- a/src/proc/mobject/session/mobjectfactory.hpp
+++ b/src/proc/mobject/session/mobjectfactory.hpp
@@ -53,8 +53,6 @@ namespace session {
   
   typedef P<asset::Track> PTrackAsset;
   
-  using asset::PSequence;
-  
   class DefsManager;
   
   
@@ -73,7 +71,7 @@ namespace session {
       Placement<Track>  operator() (PTrackAsset&);
       Placement<Effect> operator() (asset::Effect const&);
       Placement<Label>  operator() (lib::Symbol);
-      Placement<Binding>operator() (PSequence&);
+      Placement<Binding>operator() (asset::PSequence const&);
       
       ////////////////////////////////////////////////////////////////////////////////TICKET #414
     };
diff --git a/src/proc/mobject/session/session-service-mutate.hpp b/src/proc/mobject/session/session-service-mutate.hpp
new file mode 100644
index 000000000..50f62c7c5
--- /dev/null
+++ b/src/proc/mobject/session/session-service-mutate.hpp
@@ -0,0 +1,73 @@
+/*
+  SESSION-SERVICE-FETCH.hpp  -  session implementation service API: fetch PlacementRef
+ 
+  Copyright (C)         Lumiera.org
+    2008,               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.
+ 
+*/
+
+
+/** @file session-service-fetch.hpp
+ ** Implementation level session API: resolve a Placement by hash-ID.
+ ** This specialised service is intended to be used by PlacementRef,
+ ** in order to (re)-access the Placement instance within the session,
+ ** given the hash-ID of this placement. An implementation of this
+ ** service is available through the SessionServices access mechanism.
+ ** 
+ ** @see session-impl.hpp implementation of the service
+ ** @see session-services.cpp implementation of access
+ **
+ */
+
+
+#ifndef MOBJECT_SESSION_SESSION_SERVICE_FETCH_H
+#define MOBJECT_SESSION_SESSION_SERVICE_FETCH_H
+
+//#include "proc/mobject/session.hpp"
+//#include "lib/meta/generator.hpp"
+#include "proc/mobject/placement.hpp"
+
+
+
+
+namespace mobject {
+namespace session {
+  
+//  using lumiera::typelist::InstantiateChained;
+//  using lumiera::typelist::InheritFrom;
+//  using lumiera::typelist::NullType;
+  
+  /**
+   * Implementation-level service for resolving an Placement-ID.
+   * Usually, this service is backed by the PlacementIndex of the
+   * current session -- however, for the purpose of unit testing,
+   * this index may be overlaid temporarily, by using the
+   * SessionServiceMockIndex API.
+   */
+  class SessionServiceFetch
+    {
+    public:
+      static PlacementMO& resolveID (PlacementMO::ID const&) ;
+      static bool    isRegisteredID (PlacementMO::ID const&) ;
+      
+      static bool isAccessible() ;
+    };
+  
+  
+  
+}} // namespace mobject::session
+#endif
diff --git a/tests/components/proc/asset/entry-id-test.cpp b/tests/components/proc/asset/entry-id-test.cpp
index bdc7e0fff..5b28426ba 100644
--- a/tests/components/proc/asset/entry-id-test.cpp
+++ b/tests/components/proc/asset/entry-id-test.cpp
@@ -25,6 +25,8 @@
 #include "lib/test/test-helper.hpp"
 
 #include "proc/asset/entry-id.hpp"
+#include "proc/mobject/session/clip.hpp"
+#include "proc/mobject/session/track.hpp"
 #include "lib/util-foreach.hpp"
 #include "lib/symbol.hpp"
 
@@ -85,7 +87,6 @@ namespace test {
       checkCreation ()
         {
 #if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
-#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
           DummyID dID1;
           DummyID dID2("strange");
           DummyID dID3;
@@ -112,12 +113,14 @@ namespace test {
           DummyID x (dID2);  // copy ctor
           CHECK (x == dID2);
           CHECK (!isSameObject (x, dID2));
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
         }
       
       
       void
       checkBasicProperties ()
         {
+#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
           TrackID tID(" test  ⚡ ☠ ☭ ⚡  track  ");
           CHECK (tID.getIdent() == Asset::Ident("test_track", Category(STRUCT,"tracks"), "lumi", 0));
           
@@ -142,12 +145,14 @@ namespace test {
             }
           
           CHECK (sizeof (tID) == sizeof(hash::LuidH) + sizeof(Literal));
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
         }
       
       
       void
       checkComparisions ()
         {
+#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
           TrackID tID1("a1");
           TrackID tID2("a1");
           TrackID tID3("a2");
@@ -165,12 +170,14 @@ namespace test {
           CHECK (tID4 > tID3);
           
           CHECK (TrackID() < TrackID());
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
         }
       
       
       void
       checkErasure ()
         {
+#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
           TrackID tID("suspicious");
           ClipID  cID("suspicious");
           
@@ -201,12 +208,14 @@ namespace test {
           lumiera_uid_copy (&plainLUID, tID.getHash().get());
           
           CHECK (cID == ClipID::recast ("suspicious", plainLUID)); // upcast from type erased data (note: changed type)
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
         }
       
       
       void
       buildHashtable ()
         {                              //---key--+-value-+-hash-function--- 
+#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
           typedef std::tr1::unordered_map<DummyID, string, DummyID::UseEmbeddedHash()> Hashtable;
               
           Hashtable tab;
@@ -220,6 +229,7 @@ namespace test {
           CHECK (1000 == tab.size());
           
           for_each (tab.getKeys(), tab[_1] == string(_1));      /////TODO use boost::lambda to make this happen....
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #582
         }
     };
   
diff --git a/tests/lib/hash-indexed-test.cpp b/tests/lib/hash-indexed-test.cpp
index 300355865..82578715a 100644
--- a/tests/lib/hash-indexed-test.cpp
+++ b/tests/lib/hash-indexed-test.cpp
@@ -28,6 +28,8 @@
 
 #include <tr1/unordered_map>
 
+using util::isSameObject;
+
 
 namespace lib {
 namespace test{