Guideline 1
– Design a relation schema so that it is easy to
explain its meaning. Do not combine attributes
from multiple entity types and relationship types
into a single relation.
– Intuitively, if a relation schema corresponds to
one entity type or one relationship type, it is
straightforward to interpret and to explain its
meaning. Otherwise, if the relation corresponds
to a mixture of multiple entities and
relationships, semantic ambiguities will result
and the relation cannot be easily explained.