?What Is A Use Case
a usage case is simply a reason to use a System
For example ,a bank cardholder might need to use
. an ATM to get cash from their account
.It s as simple as that
The purpose of use case diagram
So in brief, the purposes of use case diagrams can be
Used to gather requirements of a system (analysis
A Use Case represents a discrete unit of interaction
between a user (human or machine) and the system
describing a system from external usage viewpoint
not developer's perspective.
Identify external and internal factors influencing the
Use case diagram components
indicates the scope of
your system. Anything
within the box
that is in scope and
anything outside the box
An actor is a person, organization, or
external system that plays a role in
one or more interactions with your
To connect between the object
A use case
value to an
The actor describes a role not person
Actors don t have to be people. They can be other
systems. For example, the ATM may need to
connect to the cardholders bank
There are two kinds of actor - primary and
Primary actor is anyone or thing that interacts with the system
to gain direct benefit.
Secondary actor is anyone or thing that involve in achieving a
use case yet, they do not gain direct benefit from the system.
Very often, secondary actor is someone who assist the
primary actor to achieve a use case.
(Use case (base
The goal must be of value to the actor .
( enter PINs( don t build ATM s just so people
can enter their PINs
A use case is an objective user(s( wants to
achieve with a system. Use cases are named
verb or verb + noun phrase.
( Continuous ….. use case(basic
Tip for use case
simple title and describe the user goal
Verbs like 'do' and 'perform' and nouns like
'data' and 'information' should be avoided
It is intended to provide an overview of what the
user want without knowing how to achieve the
(Continuous ….. use case( not basic
The <<include>> use case means that the
flow of that use case is always included
But a <<extend>> use case means that the
flow of the extending use case is only
included under specific conditions
the key questions we need to ask are;
who will be using the system, and what will
they be using it to do?
Be one of the smart 1% and always
remember that use case designs aren t the
same thing as requirements
Do not try to include all types of relationships.
Because the main purpose of the diagram is
to identify requirements.