Move common factors up the hierarchy
From CSSEMediaWiki
- Factor the commonality of data, behavior, and/or interface as high as possible in the inheritance hierarchy.. --Riel's Heuristic , Arthur Riel 1996
Any behavior that is shared between all subclasses can logically be promoted to their superclass. If you find yourself moving factors up the hierarchy it may be worth the time to review your design and consider why this inheritance was not spotted at first.
