%
% move current task to the sought position
%
_Chain.Back any?
{
%
% move from current task tree
% back to a common node with the target tree
%
% compare the destination string to the current task tree
%
 @@
 _@
 true compare
%
% stack: difference position
% the new position will be one beyond
% the length of the current tree name
%
 pop2nd _@ length) gt
 {
%
% the strings match to the current task tree
%
  _Chain.Back _@ length) + fromleft
%
% now we need to move downward to the destination
%
  !Chain.Forward
  empty !Chain.Back
 }
 {
%
% seek and task tree strings don't match to the current tree
%
  "#" _@ Str.Found
  {
%
% this is sub-tree, need to move back up the chain
%
   "Back" vector()
  }
  {
%
% at the apex of the Tree system
% must be within Default Tree
% entire seek string is forward target
%
   _Chain.Back !Chain.Forward
   empty !Chain.Back
  } ifelse
 } ifelse
 "taskchin" chain(
}
{
%
% check for any forward steps needed
%
 _Chain.Forward any?
 {
%
% there are steps remaining for forward arrival
%
% seek the tree specified in the hierarchy destination
% by descending to the next destination point
%
% descend to the next step
%
  "Via" vector()
  !Chain.Forward

  "taskchin" chain(
 }
 {
%
% no more chain steps
% 
% retract the Chain survey layer
%
  false "Chain" Task.Survey

 } ifelse
} ifelse