Database Reference
In-Depth Information
•
Can an
Employee
have more than one
Phone Number
?
•
Can an
Employee
have more than one
Employee Name
?
•
Can an
Employee
have more than one
Department Name
?
•
Can an
Employee
have more than one
Employee Start Date
?
•
Can an
Employee
have more than one
Employee Vested Indicator
?
•
Separate multi-valued attributes
.
Multi-valued
means that within the same at-
tribute we are storing at least two distinct values. There are at least two different
business concepts hiding in one attribute. For example,
Employee Name
may con-
tain both a first name and last name.
Employee First Name
and
Employee Last
Name
can be considered distinct attributes, and therefore
Henry Winkler,
stored in
Name, is multi-valued, because it contains both
Henry
and
Winkler
. We may find
ourselves asking many questions just to determine if there are any multi-valued at-
tributes we need to identify. We can have another question template, such as “Does
a [[insert attribute name here]] contain more than one piece of business informa-
tion?” So these are all valid questions in our employee example:
•
Does an
Employee Identifier
contain more than one piece of business information?
•
Does a
Department Code
contain more than one piece of business information?
•
Does a
Phone Number
contain more than one piece of business information?
•
Does an
Employee Name
contain more than one piece of business information?
•
Does a
Department Name
contain more than one piece of business information?
•
Does an
Employee Start Date
contain more than one piece of business information?
•
Does an
Employee Vested Indicator
contain more than one piece of business information?
After answering these questions based on the earlier set of sample data, and by talking with
a business expert, we can update the model: