Unified Modeling Language

(UML)

UML

• Graphical notation to support expressing Object-Oriented Designs in a compact form• Notation is quite expressive, includes many different

types of diagrams, and can be used to generate code

• We will use Class diagrams from UML• Capture a high level description of a class as well as

the relationships with other classes.

Simple text notation

• The UML diagrams have a simple text notation to indicate visibility.

• Consider a class with a member variable of type String called “name”

Notation Meaning Example

- private - name : String

+ public + name : String orname : String

# protected # name : String

Graphical Notations

• Class diagram• Name on top, usually

bolded• Attributes are member vars• Operations are methods

• Interface diagram• Adds the stereotype

designation <<interface>>

Inheritance

• Inheritance relates two classes

• One class is defined as an extension of the other• Existing one is called: base

class, superclass• New class called: subclass,

or derived class

• Connected in diagram with arrow with white triangle

Aggregation

• One class is made up of others (aggregation of objects)

• BigClass is defined in terms of other classes• Some of member vars are

objects of another class

Association

• Relationship between objects• Different from aggregation

because objects are considered “complete”whether the association is in place or not.

• Example: student object has an association with several course sections, the ones that she is registered in.

• Can have cardinality

Association

• Sometimes the association is an object by itself

• Often when the association holds data

• Example: employment associates Person with Company, includes information about employment date, position title, etc.