Introduction
to Software Engineering
(Introduction to UML and Use Case Diagram)
Objective
·
Study the benefits of visual modeling.
·
Learn use case diagrams:
o discovering actors
o discovering use cases.
·
Practice use cases diagrams
Outline
Visual
modeling.
Introduction
to UML.
Introduction
to visual modeling with UML.
Use case
diagrams: discovering actors and use cases.
Background
Visual Modeling is a way of thinking about problems using models
organized around real-world ideas. Models are useful for understanding
problems, communicating with everyone involved with the project (customers,
domain experts, analysts, designers, etc.), modeling enterprises, preparing
documentation, and designing programs and databases.
Visual Modeling
·
Capture the structure and behavior of architectures
and components.
·
Show how the elements of the system fit together.
·
Hide or expose details appropriate for the task.
·
Maintain consistency between a design and its
implementation.
·
Promote unambiguous communication.
What is UML?
The UML is the standard language for visualizing, specifying,
constructing and documenting the artifacts of a software-intensive system. UML
can be used with all processes throughout the development life cycle and across
different implementation technologies.
Putting UML into
Work: Use Case Diagram
The behavior of the system under development (i.e. what functionality
must be provided by the system) is documented in a use case model that
illustrates system's intended functions (use cases), its surroundings (actors),
and relationships between the use cases and actors (use case diagrams).
Actors
·
Are NOT part of the system – they represent anyone
or anything that must interact with the system.
·
Only input information to the system.
·
Only receive information from the system.
·
Both input to and receive information from the
system.
·
Represented in UML as a stick man.
 |
| Actors |
Use Case
A
sequence of transactions performed by a system that yields a measurable result
of values for a particular actor.
A use
case typically represents a major piece of functionality that is complete from
beginning to end. A use case must deliver something of value to an actor.
 |
| UseCase |
Use Case
Relationships
·
Between actor and use case.
·
Association / Communication.
·
Arrow can be in either or both directions; arrow
indicates who initiates communication.
·
Between use cases (generalization):
o
Uses
§ Where multiple use cases share pieces of same functionality.
o
Extends
§ Optional behavior.
§ Behavior only runs under certain conditions (such as alarm).
§ Several different flows run based on the user’s selection.
Exercise
We are after a system that controls a recycling machine for returnable
bottles and cans. The machine will allow a customer to return bottles or cans
on the same occasion.
When the customer returns an item, the system will check what type has
been returned. The system will register how many items each customer returns
and, when the customer asks for a receipt, the system will print out what he
deposited, the value of the returned items and the total return sum that will
be paid to the customer.
The system is also be used by an operator. The operator wants to know how
many items of each type have been returned during the day. At the end of the
day, the operator asks for a printout of the total number of items that have
been deposited in the machine on that particular day. The operator should also
be able to change information in the system, such as the deposit values of the
items. If something is amiss, for example if a can gets stuck or if the receipt
roll is finished, the operator will be called by a special alarm signal.
After reading the
above problem statement, find
1. Actors
2. Use cases with each actor
3. Find extended or uses use cases (if applicable)
4. Draw the main use case diagram
You should use these techniques to draw use case diagrams for your
semester project
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