diff --git a/src/proc/engine/job-planning.hpp b/src/proc/engine/job-planning.hpp
index e4f6203ed..dbdcc8c52 100644
--- a/src/proc/engine/job-planning.hpp
+++ b/src/proc/engine/job-planning.hpp
@@ -60,8 +60,8 @@ namespace engine {
    */ 
   class JobPlanning
     {
-      JobTicket::iterator plannedOperations_;
-      FrameCoord point_to_calculate_;
+      JobTicket::ExplorationState plannedOperations_;
+      FrameCoord                 point_to_calculate_;
      
     public:
       /** by default create the bottom element of job planning,
@@ -71,12 +71,11 @@ namespace engine {
       JobPlanning()
         { }
       
-      /** further job planning can be initiated by continuing
-       * off a given previous planning state. This is how
-       * the forks are created, expanding into a multitude
-       * of prerequisites of a given job
+      /** further job planning can be initiated by continuing off a given previous planning state.
+       *  This is how the forks are created, expanding into a multitude of prerequisites for
+       *  the job in question.
        */
-      JobPlanning (JobTicket::iterator const& startingPoint, FrameCoord requestedFrame)
+      JobPlanning (JobTicket::ExplorationState const& startingPoint, FrameCoord requestedFrame)
         : plannedOperations_(startingPoint)
         , point_to_calculate_(requestedFrame)
         { }
@@ -112,6 +111,9 @@ namespace engine {
                                ,this->point_to_calculate_);
         }
       
+      /** integrate another chain of prerequisites into the current evaluation line.
+       *  Further evaluation will start to visit prerequisites from the new starting point,
+       *  and return to the current evaluation chain later on exhaustion of the side chain. */
       friend void
       integrate (JobPlanning const& newStartingPoint, JobPlanning existingPlan)
       {
@@ -137,7 +139,7 @@ namespace engine {
       friend void
       iterNext (JobPlanning & plan)
       {
-        ++(plan.plannedOperations_);
+        plan.plannedOperations_.pullNext();
       }      
     };
   
@@ -192,8 +194,6 @@ namespace engine {
             //                  (which is a JobPlanning) can stand-in for the sequence of prerequisites
         }
       
-      ///TODO what elements are accepted by the explorationStack? provide conversion operator to extract those from stateCore()
-      
       
       
       /** Extension point to be picked up by ADL.
diff --git a/src/proc/engine/job-ticket.hpp b/src/proc/engine/job-ticket.hpp
index 6a13df71f..56148907d 100644
--- a/src/proc/engine/job-ticket.hpp
+++ b/src/proc/engine/job-ticket.hpp
@@ -117,15 +117,10 @@ using lib::LinkedElements;
       LinkedElements<Prerequisites> requirement_;
       
       
+    public:
       class ExplorationState;
       friend class ExplorationState;
       
-      struct TraversalOfPrerequisites;
-        
-    public:
-        
-      typedef TraversalOfPrerequisites iterator;
-      
       
       JobTicket()
         {
@@ -133,7 +128,7 @@ using lib::LinkedElements;
         }
       
       
-      iterator discoverPrerequisites()  const;
+      ExplorationState discoverPrerequisites()  const;
       
       Job createJobFor (FrameCoord coordinates);
       
@@ -157,42 +152,39 @@ using lib::LinkedElements;
       // using default ctor and copy operations
       
       
+      bool
+      empty()  const
+        {
+          UNIMPLEMENTED ("detect empty/no prerequisites");
+        }
       
-      /* === Iteration control API for IterStateWrapper== */
-  
-      friend bool
-      checkPoint (ExplorationState const& plan)
-      {
-        UNIMPLEMENTED ("detect end of prerequisites");
-      }
       
-      friend JobTicket&
-      yield (ExplorationState const& plan)
-      {
-        UNIMPLEMENTED ("access prerequisite and follow up to prerequisite JobTicket");
-      }
-      
-      friend void
-      iterNext (ExplorationState & plan)
-      {
-        UNIMPLEMENTED ("step ahead to next prerequisite");
-      }      
-    };
-    
-  
-  struct JobTicket::TraversalOfPrerequisites
-    : lib::IterStateWrapper<JobTicket, JobTicket::ExplorationState>
-    {
       void
-      push (TraversalOfPrerequisites subExploration)
+      pullNext()
+        {
+          UNIMPLEMENTED ("step ahead to next prerequisite, maybe pop");
+        }
+      
+      void
+      push (ExplorationState subExploration)
         {
           UNIMPLEMENTED ("integrate a branch of prerequisites");
         }
       
+      
+      JobTicket*
+      operator->() const
+        {
+          UNIMPLEMENTED ("yield the current job ticket");
+          // access prerequisite and follow up to prerequisite JobTicket
+        }
+      
     };
+    
   
   
-  inline JobTicket::iterator
+  
+  inline JobTicket::ExplorationState
   JobTicket::discoverPrerequisites()  const
   {
     UNIMPLEMENTED("delve into the requirement_ datastructure");