Database Reference
In-Depth Information
Defining the Mission Objectives
To expand upon the overview in the previous chapter, mission objectives are statements
that represent the general tasks supported by the data maintained in the database. Each
mission objective represents a single task. These mission objectives provide information
that you'll use throughout the database design process. For example, mission objectives
helpyoudefinetablestructures,fieldspecifications,relationshipcharacteristics,andviews.
They also help you establish data integrity and define business rules. Finally, mission ob-
jectives guide your development efforts and ensure that your final database structure sup-
ports the mission statement.
Well-Written Mission Objectives
Awell-writtenmissionobjectiveisadeclarativesentencethatclearlydefinesageneraltask
and is free from unnecessary details. It is expressed in general terms, succinct and to the
point, and unambiguous. Here are some examples of typical mission objectives:
Maintain complete patient address information.
Keep track of all customer sales.
Make sure an account representative is responsible for no more than 20 accounts at
any given time.
Keep track of vehicle maintenance.
Produce employee phone directories.
These mission objectives are well defined and easy to understand. Each mission objective
representsasinglegeneraltaskanddefinesthetaskclearlywithoutunnecessarydetails.For
example, the last mission objective in the list states that employee directories need to be
produced,butitdoesn'tindicate how theyaretobeproduced.Itisnotnecessarytoindicate
how the employee directories will be produced because that issue is part of the application
development process. Remember that the purpose of a mission objective is to help define
various structures within the database and to help guide the overall direction of the data-
base's development.
If a mission objective represents more than one general task, you should decompose it into
two or more mission objectives. Here is an example of a poorly written mission objective:
We need to keep track of the entertainers we represent and the
type of entertainment they provide, as well as the engagements
that we book for them.
There are two problems with this mission objective.
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