anchor.diff:  	{ok, {string, Bin}} ->
   	    case make_cid(Dict, to_atom(Bin)) of
   		#occi_cid{}=Cid ->
  -		    case occi_category_mgr:get(Cid) of
  +		    try occi_category_mgr:get(Cid) of
   			#occi_kind{}=Kind ->
   			    new_entity(Kind, V, H, S);
   			#occi_mixin{}=Mixin ->
  -			    add_mixin(Mixin, V, H, S)
  +			    add_mixin(Mixin, V, H, S);
  +			_ ->
  +			    {error, {einval, Cid}}
  +		    catch
  +			throw:Err ->
  +			    {error, Err}
   		    end;
   		{ok, Val} ->
   		    {error, {einval, Val}};
  
positive.code: 	{ok, #state{action=Action}} ->
  	    {ok, Action};
  	{error, Err} ->
  	    {error, Err}
      end.
  
  parse_entity(Headers, #state{}=State) ->
  
negative.code: 	{ok, {string, <<"action">>}} ->
  	    case make_cid(Dict, action) of
  		#occi_cid{}=Cid ->
  		    try occi_category_mgr:get(Cid) of
  			#occi_action{}=A ->
  			    parse_attributes(H, S#state{action=A});
  			_ ->
  			    {error, invalid_category}
  		    catch
  			throw:Err ->
  			    {error, Err}
  		    end;
  		{error, Err} ->
  		    {error, Err}
  