The ABSTRACT_BACKTRACKING uses the fields
continuation to record the continuation path
and calls the feature 'next_sequence' to let
the current object choose how to continue the
exploration.
Called by ABSTRACT_BACKTRACKING to let
the current object switch to the next state
to explore.
Two actions must be performed by that feature:
- make iteration actions and then call
'pop_sequence' if this is the last state
to be explored.
- select the state to be evaluated or
call 'continue' or call 'backtrack'.