Database Reference
In-Depth Information
Can a Check exist without a Check Debit?
✓
Can a Check Debit exist without a Check?
✓
Are there examples of Check that would be valuable to show?
✓
Does a Check go through a lifecycle?
✓
I shaded in sets of rows to make it easier to read the questions for each relationship set.
With the answers to these questions, we have enough information to build the conceptu-
al data model. For example, we can model the answers to the first four questions between
Customer
and
Account
:
•
Each
Customer
may own one or many
Accounts
.
•
Each
Account
must be owned by one or many
Customers
.
Walk through the first four questions and see how it leads to this model. If you need a re-
fresher on cardinality (those symbols on the relationship lines), please refer back to Chapter
3.
Note that often after answering these questions, we uncover new entities. For example,
because “Yes” was checked for
Are there examples of Account that would be valuable to
show?
, we will most likely show several examples of
Account
as subtypes of
Account
on
the model. Because “Yes” was checked for
Does a Customer go through a lifecycle?
, we
will most likely show the lifecycle of
Customer
as subtypes of
Customer
on the model.
Adding new subtypes means defining each subtype and also refining some of the questions
that are asked to the business expert, which leads to refining some of the relationships on
the resulting model. For example, if we add a
Checking Account
subtype to
Account
, it is
possible that
Check Debit
just applies to
Checking Account
and not to all accounts such
as
Savings Account
.
For Dimensional
