diff --git a/src/proc/mobject/session.hpp b/src/proc/mobject/session.hpp
index 72a213907..4bab5f285 100644
--- a/src/proc/mobject/session.hpp
+++ b/src/proc/mobject/session.hpp
@@ -129,14 +129,14 @@ namespace mobject {
       TimelineAccess timelines;                 ///< collection of timelines (top level)
       SequenceAccess sequences;                 ///< collection of sequences
       
-      virtual bool isValid ()                    = 0;
-      virtual MObjectRef attach (PMO& placement) = 0;
-      virtual bool       detach (PMO& placement) = 0;
+      virtual bool isValid ()                          = 0;
+      virtual MObjectRef attach (PMO const& placement) = 0;
+      virtual bool       detach (PMO const& placement) = 0;
       
-      virtual MObjectRef getRoot()               = 0;
+      virtual MObjectRef getRoot()                     = 0;
       
-      virtual session::PFix& getFixture ()       = 0;
-      virtual void rebuildFixture ()             = 0;
+      virtual session::PFix& getFixture ()             = 0;
+      virtual void rebuildFixture ()                   = 0;
       
     };
   
diff --git a/src/proc/mobject/session/binding.cpp b/src/proc/mobject/session/binding.cpp
index 955d94149..eac8d70ea 100644
--- a/src/proc/mobject/session/binding.cpp
+++ b/src/proc/mobject/session/binding.cpp
@@ -32,7 +32,7 @@ namespace session {
     : boundSequence_(sequence_to_bind)
     {
       throwIfInvalid();
-      UNIMPLEMENTED ("what additionally to do when binding a sequence??");
+      TODO ("what additionally to do when binding a sequence??");
     }
   
   
diff --git a/src/proc/mobject/session/query-focus.hpp b/src/proc/mobject/session/query-focus.hpp
index 1fed6da2a..3dfe9ba04 100644
--- a/src/proc/mobject/session/query-focus.hpp
+++ b/src/proc/mobject/session/query-focus.hpp
@@ -27,6 +27,7 @@
 #include "proc/mobject/session/scope-path.hpp"
 #include "proc/mobject/session/scope-query.hpp"
 #include "proc/mobject/session/scope-locator.hpp"
+#include "proc/mobject/placement-ref.hpp"
 
 #include <boost/intrusive_ptr.hpp>
 #include <string>
@@ -91,6 +92,7 @@ namespace session {
       QueryFocus();
       
       ScopePath const& currentPath()  const;
+      RefPlacement     currentPoint() const;
       operator Scope()                const;
       operator string()               const;
       
@@ -144,6 +146,15 @@ namespace session {
     return *focus_;
   }
   
+  /** @return placement-ref to the object the
+   *          QueryFocus is currently pointing at
+   */
+  inline RefPlacement
+  QueryFocus::currentPoint() const
+  {
+    return RefPlacement (focus_->getLeaf().getTop());
+  }
+  
   
   /** discover depth-first any matching object
    *  within \em current focus. Resolution is
diff --git a/src/proc/mobject/session/session-impl.cpp b/src/proc/mobject/session/session-impl.cpp
index becf042f2..6ce106049 100644
--- a/src/proc/mobject/session/session-impl.cpp
+++ b/src/proc/mobject/session/session-impl.cpp
@@ -23,10 +23,13 @@
 
 #include "proc/mobject/session/session-impl.hpp"
 #include "proc/mobject/session/mobjectfactory.hpp"
+#include "proc/mobject/session/query-focus.hpp"
 #include "proc/mobject/placement.hpp"
 #include "proc/mobject/mobject.hpp"
 #include "lib/error.hpp"
 
+using namespace lumiera;
+
 namespace mobject {
 namespace session {
   
@@ -63,7 +66,7 @@ namespace session {
       }
     catch (...)
       {
-        throw lumiera::error::Fatal ("unexpected exception while clearing the session"); ///////////TODO still required??
+        throw error::Fatal ("unexpected exception while clearing the session");          ///////////TODO still required??
       }
   }
   
@@ -75,25 +78,58 @@ namespace session {
   }
   
   
+  
+  /** attach a copy within the scope
+   *  of the current QueryFocus point
+   *  @return reference to the newly created
+   *          instance (placement) which was attached
+   *          below the position given by current focus
+   */
   MObjectRef 
-  SessionImpl::attach (PMO& placement)
+  SessionImpl::attach (PMO const& placement)
   {
-    UNIMPLEMENTED ("add Placement to the current Session");
+    MObjectRef newAttachedInstance;
+    RefPlacement attachmentPoint = QueryFocus().currentPoint();
+    newAttachedInstance.activate(
+        contents_.insert (placement, attachmentPoint));
+    return newAttachedInstance;
   }
   
   
+  /** detach the denoted object (placement) from model,
+   *  together with any child objects contained in the
+   *  scope of this placement. 
+   *  @note as a sideeffect, the current QueryFocus
+   *        is moved to the scope containing the
+   *        object to be removed
+   *  @throw error::Invalid when attempting to kill root
+   *  @return \c true if actually removing something
+   */
   bool 
-  SessionImpl::detach (PMO& placement)
+  SessionImpl::detach (PMO const& placement)
   {
-    UNIMPLEMENTED ("search and remove a given Placement from current Session");
-    return false; // TODO
+    bool is_known = contents_.contains (placement);
+    if (is_known)
+      {
+        if (Scope(placement).isRoot())
+          throw error::Invalid ("Can't detach the model root."
+                               , LUMIERA_ERROR_INVALID_SCOPE);
+        
+        QueryFocus currentFocus;
+        currentFocus.attach (Scope(placement).getParent());
+        contents_.clear (placement);
+      }
+    ENSURE (!contents_.contains (placement));
+    return is_known;
   }
   
   
   MObjectRef
   SessionImpl::getRoot()
   {
-    UNIMPLEMENTED ("access and return the model root, packaged as MObject-ref");
+    MObjectRef refRoot;
+    refRoot.activate (contents_.getRoot());
+    return refRoot;
   }
 
   
diff --git a/src/proc/mobject/session/session-impl.hpp b/src/proc/mobject/session/session-impl.hpp
index e0bec4767..c741bde80 100644
--- a/src/proc/mobject/session/session-impl.hpp
+++ b/src/proc/mobject/session/session-impl.hpp
@@ -84,8 +84,8 @@ namespace session {
       
       /* ==== Session API ==== */
       virtual bool isValid ();
-      virtual MObjectRef attach (PMO& placement);
-      virtual bool       detach (PMO& placement);
+      virtual MObjectRef attach (PMO const& placement);
+      virtual bool       detach (PMO const& placement);
       
       virtual MObjectRef getRoot();