The finish line in a race is there as a reference point for the racers, the judges and the audience. This is true for track and field, auto racing and horse racing. Its key characters? It is clearly defined and does not move. So as the race participants run over it,it is possible to determine who won the race. Likewise a controlled variable in any valid experiment is clearly defined and does not change. They are both static reference point.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.