Properly created data models are intended to be read as a series of English
(or other) language assertions about the business. Each relationship can
be translated into two sentences -- one reading from each end. The structure
of each sentence is:
- Each
- <<1st entity name>>
- must be or may be
- << relationship name >>
- one and only one or one or more
- <<2nd entity name>>
- .
For example, in Figure 1, below, the relationship reads from right to left,
"Each ORDER may be composed of one
or more LINE ITEMS." From left to right, it reads,
"Each LINE ITEM must be part of one
and only one ORDER.
Figure 1: Sample Model