Database Reference
In-Depth Information
Will this rule be violated if I
do not
enter a value into this field?
Will this rule be violated if I update the value of this field?
Will this rule be violated if I delete the value of this field?
Once you've determined which actions will trigger a violation of the rule, make note of
them; you'll use them in the next step. This information will also help you to establish
this rule in the most effective manner possible when you implement the database in your
RDBMS.
Inthiscase,thebusinessrulefortheC
UST
C
OUNTY
fieldwillbetestedwhenyoutryto
insert
a value into the field because the value must be within a specific range of values. The rule
will also be tested when you try to
delete
a value in the field because the value cannot be
null.
Step 6: Record the Rule on a Business Rule Specifications Sheet
You can document a given business rule for future reference by filling out a Business Rule
Specifications sheet. This is something you should do for every rule, regardless of its type
or category. The Business Rule Specifications sheet provides three advantages.
1.
It allows you to document every database-oriented business rule.
This helps you
ensure that you have appropriately defined and properly established each rule.
2.
It allows you to document every application-oriented business rule.
Although you
cannot
establish
this type of rule within the logical design of the database, you can
at least indicate its basic elements. The information you document for this type of
business rule will prove invaluable to you when you implement the database with-
in your RDBMS or when you create the application program that people will use
to work with the database.
3.
It provides a standard method for recording all business rules.
Business rules are
easier to track and maintain if you record them in a consistent manner. Using a uni-
form format also makes it easier for you to troubleshoot business rules; every as-
pect of the rule appears on the specification sheet.
The Business Rule Specifications sheet contains the following items.
•
Statement:
This is the text of the business rule itself. It should be clear and succinct
and should convey the required constraints without any confusion or ambiguity.
Here's an example of a well-framed statement:
A booking agent cannot be assigned to more than 25 entertainers.
•
Constraint:
This is a brief explanation of how the constraint applies to the tables
and fields. For instance, you can use the following explanation for the constraint
imposed by the business rule in the preceding example:
