>You can define abstract classes but there is no language enforcement that the methods remain empty.
True, but you can fake it (sort of...<g>)

function AbstractWarn()
  local lcSetAssert
  lcSetAssert = set("Assert")
  set Assert on
  assert .f. Message Program() + " should be overwritten !"
  set Assert &lcSetAssert

define class GraphicAbstractObject as custom
   x = 0
   y = 0

function moveTo( newX, newY )
  = AbstractWarn()
endfunc

function draw()
  = AbstractWarn()
endfunc

enddefine

regards

thomas