3.6.1.1 Removing Ternary relationship types
It is advantageous to remove ternary and higher order relationship types. One reason is that it
might be considered more `natural' to think of entity types having attributes than relationship
types having them. It is in fact always possible to remove these high-order relationship types and
replace them with an entity type. A ternary relationship type is then replaced by an entity type
and three binary relationship types linking it to the entity types which were originally linked by
the ternary. A quartenary relationship type would be replaced by an entity type and four
relationship types and so on.
In Fig. 3.8(e), the ternary relationship type 'recommends' (verb) can be replaced with an entity
type 'recommendation' (noun), and a binary relationship between it and each of the entity types
LECTURER, TEXT and COURSE (three binary relationships in all). It is natural to think about
the attributes of a recommendation but not so natural to think about the attributes of a