diff --git a/src/proc/engine/job-ticket.cpp b/src/proc/engine/job-ticket.cpp
index 317bccc18..e5bec3783 100644
--- a/src/proc/engine/job-ticket.cpp
+++ b/src/proc/engine/job-ticket.cpp
@@ -45,7 +45,6 @@ namespace engine {
 //  using mobject::session::Effect;
   
   
-  JobClosure::~JobClosure() { }
   
   
   
diff --git a/src/proc/engine/job-ticket.hpp b/src/proc/engine/job-ticket.hpp
index edd7c4bd2..8909c87e5 100644
--- a/src/proc/engine/job-ticket.hpp
+++ b/src/proc/engine/job-ticket.hpp
@@ -52,28 +52,6 @@ using util::isnil;
 //  
 //class ExitNode;
   
-  /** 
-   * a job closure represents the execution context of a job.
-   * This allows us to enqueue simple job-"functions" with the scheduler.
-   * By virtue of the JobClosure-pointer, embedded into #lumiera_jobDefinition,
-   * the invocation of such a job may re-gain the full context, including the
-   * actual ProcNode to pull and further specifics, like the media channel.
-   */ 
-  class JobClosure
-    : public lumiera_jobClosure
-    {
-    public:
-      virtual ~JobClosure();     ///< this is an interface
-      
-      
-      virtual void invokeJobOperation (JobParameter parameter)  =0;
-      virtual void signalFailure      (JobParameter parameter)  =0;
-      
-      virtual JobKind getJobKind()  const                       =0;
-      virtual bool verify (Time nominalJobTime)  const          =0;
-    };
-  
-  
   
   /**
    * execution plan for pulling a specific exit node.
diff --git a/src/proc/engine/job.cpp b/src/proc/engine/job.cpp
index 8db0a5c77..f92001d8f 100644
--- a/src/proc/engine/job.cpp
+++ b/src/proc/engine/job.cpp
@@ -57,6 +57,18 @@ namespace engine {
 //  using mobject::session::Effect;
   
   
+  
+  /**
+   * emit the VTable for JobClosure within this compilation unit,
+   * which is still part of the backend. The actual job implementation
+   * classes are defined in the Proc-Layer
+   */
+  JobClosure::~JobClosure() { }
+  
+  
+  
+  
+  
   /** @todo WIP-WIP 2/12  
    */
   void
diff --git a/src/proc/engine/job.hpp b/src/proc/engine/job.hpp
index 461fa95c8..d100003ec 100644
--- a/src/proc/engine/job.hpp
+++ b/src/proc/engine/job.hpp
@@ -133,7 +133,7 @@ namespace engine {
   
   
   /**
-   * Frame rendering task, represented as closure.
+   * Individual frame rendering task, forwarding to a closure.
    * This functor encodes all information necessary to trigger
    * and invoke the actual rendering operation. It will be embedded
    * by value into a job descriptor and then enqueued with the scheduler
@@ -182,6 +182,35 @@ namespace engine {
     };
   
   
+  /**
+   * Interface of the closure for frame rendering jobs.
+   * Hidden behind this interface resides all of the context re-building
+   * and invocation mechanics to get the actual calculations going. While
+   * the job descriptor, as handled by the scheduler, contains the variable
+   * "moving parts", the corresponding job closure represents the execution
+   * context of a job and is shared between several jobs within the same
+   * segment of the timeline.
+   * 
+   * This allows us to enqueue simple job-"functions" with the scheduler.
+   * By virtue of the JobClosure-pointer, embedded into #lumiera_jobDefinition,
+   * the invocation of such a job may re-gain the full context, including the
+   * actual ProcNode to pull and further specifics, like the media channel.
+   */
+  class JobClosure
+    : public lumiera_jobClosure
+    {
+    public:
+      virtual ~JobClosure();     ///< this is an interface
+      
+      
+      virtual void invokeJobOperation (JobParameter parameter)  =0;
+      virtual void signalFailure      (JobParameter parameter)  =0;
+      
+      virtual JobKind getJobKind()  const                       =0;
+      virtual bool verify (Time nominalJobTime)  const          =0;
+    };
+  
+  
 }} // namespace proc::engine