se_lec 07_uml class diagram

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The class diagram is a static model that shows the

classes and the relationships among classes in the

system.

Class diagrams illustrates classes, interfaces, and their

associations. They are used for static object modeling.

A Class diagram gives an overview of a system by

showing its classes and the relationships among them.

Class diagrams display what interacts but not what

happens when they do interact

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The main building block of a class diagram is the class,

which stores and manages information in the system.

A blueprint that an object made from.

The class contains two major parts:

• Attributes “data members”.

• Operations “method members”.

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No arrows; info can

flow in both directions

Aggregation – Order class

contains OrderDetail classes.

Could be composition?

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Class diagrams are great for:

discovering related data and attributes

getting a quick picture of the important entities in a system

seeing whether you have too few/many classes

seeing whether the relationships between objects are too

complex, too many in number, simple enough, etc.

spotting dependencies between one class/object and another

Not so great for:

discovering algorithmic (not data-driven) behavior

finding the flow of steps for objects to solve a given problem

understanding the app's overall control flow (event-driven? web-

based? sequential? etc.)

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Draw a class diagram for a information modeling systemfor a school.

School has one or more Departments.

Department offers one or more Subjects.

A particular subject will be offered by only onedepartment.

Department has instructors and instructors can workfor one or more departments.

Student can enrol in upto 5 subjects in a School.

Instructors can teach upto 3 subjects.

The same subject can be taught by differentinstructors.

Students can be enrolled in more than one school.

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School has one or more Departments.

School Departmenthas1 1..*

Department offers one or more Subjects.

A particular subject will be offered by only one department.

Department Subjectoffers1 1..*

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Department has Instructors and instructors can work

for one or more departments.

assigned to1..*

Instructor Department1..*

Student can enrol in upto 5 Subjects.

Student Subjecttakes* 0..5

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Instructors can teach up to 3 subjects.

The same subject can be taught by different

instructors.

Instructor Subjectsteaches

1..*

1..3

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Students can be enrolled in more than one school.

Student Schoolmember

*

1..*

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School Department

Student Subject Instructor

1…*

*

member

* 1..5

attends

1..3 1..*

teaches

1..*

1

1 1..*

has

1..*

1..*

assignedTo

offeres

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Object Diagram shows the relationship between objects.

Unlike classes objects have a state.

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c1: Company

d2: Departmentd1: Department

name=“Sales” name=”CSSE”

p1: Persont

name=“Rao”

p2: Person

name=“Raj”

manager employee

c1: Company

name=“UniMelb”

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