anchor.diff:    result := nil;
     if (prop = 'concept') and StringIsId(value, id) then
       if op = foIsA then
  -      result := filterIsA(id)
  +      result := filterIsA(id, true)
  +    else if op = foDescendentOf then
  +      result := filterIsA(id, false)
       else if op = foIn then
         result := filterIn(id);
   end;
  
positive.code:     FEditionName : String;
  
      function filterIn(id : UInt64): TCodeSystemProviderFilterContext;
      function filterIsA(id : UInt64): TCodeSystemProviderFilterContext;
  
    //  Function FindWord(s : String; var index : Integer) : Boolean;
      Function FindStem(s : String; var index : Integer) : Boolean;
  
negative.code:   try
      if not Concept.FindConcept(id, index) then
        raise ETerminologyError.Create('The Snomed Concept '+inttostr(id)+' was not known');
      if includeBase then
        res.descendants := mergeCardinals(index, GetConceptDescendants(index))
      else
        res.descendants := GetConceptDescendants(index);
      result := TSnomedFilterContext(res.link);
    finally
      res.Free;
  