UML

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UML Class DiagramsLesson - 9
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Objectives

• What is UML?
• UML Diagrams
• Use Case Diagram
• Class Diagram

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What is UML?

• The Unified Modeling Language (UML) is a
  standard  language for specifying, visualizing,
  constructing, and documenting the artifacts of
  software systems, as well as for business
  modeling and other non-software systems.
• UML uses graphical notations to express the
  design of software projects.
• Modeling is necessary for readability and reuse
  of systems.

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UML Diagrams

• UML modeling consists of nine different diagrams
  to model a software system.
• Each UML diagram is designed to let developers
  and customers view a software system from a
  different perspective and in varying degrees of
  abstraction.

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UML Diagrams

• Use case Diagram
• Class Diagram
• Object Diagram
• State Diagram
• Activity Diagram
• Sequence Diagram
• Collaboration diagram
• Component diagram
• Deployment diagram

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Use case Diagram

• Use case diagram displays the relationship among
  actors and use cases.
• Actors An actor is any entity that performs
  certain roles in a given system. For example, In
  a banking application, a customer entity
  represents an actor. Similarly, the person who
  provides service at the counter is also an actor.
  

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Use case Diagram

• Use Case A use case in a use case diagram is a
  visual representation of a distinct business
  function in a system. For example, In a banking
  application, a deposit function represents a use
  case.
• To identify use cases, you should list the
  discrete business functions the user might do in
  order to complete an action.
• For a banking application it might be
• deposit money
• withdraw money

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Use case Diagram
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Class Diagram

• Class diagrams model class structure and contents
  using design elements such as classes, packages
  and objects.
• A class diagram is a diagram showing a collection
  of classes and interfaces, along with the
  collaborations and relationships among classes
  and interfaces.
• A class diagram is composed of
• Class A class has a business functionality
  called methods, and properties that reflect
  unique features of a class. The properties of a
  class are called attributes.

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Class Diagram

• For example Let us take a class named Student.
  The Student class encapsulates student
  information such as student id , student name,
  and so forth. Student id, student name, and so on
  are the attributes of the Student class. The
  Student class also exposes functionality to other
  classes by using methods such as
  getStudentName(), getStudentId(), and the like.
  Let us take a look at how a class is represented
  in a class diagram.

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Class Diagram

• The following diagram shows a typical class in a
  class diagram

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Elements of a Class Diagram

• Attributes correspond to the class level
  variables (but not variables declared within the
  body of a method).
• Operations correspond to methods in Java.
• Public members (attributes or operations) can be
  referenced directly by any classes in this or any
  other model package (more on packages later).
• Private members can only be referenced in the
  same class where theyre declared.
• Protected members can be referenced in the same
  class or in any descendants of that class (more
  on inheritance later).
• Package scope members can be referenced by any
  classes in the same UML package only.

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Access Specifiers
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Static Members
Static members can be referenced without
instantiating the class to which they belong.
In UML, static members are underlined.
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Abstract Classes

• Abstract classes are partially implemented and
  force us to extend it before we can use its
  functionality. In class diagrams, the name of an
  abstract class is specified in italics
• Abstract methods that must be implemented in
  subclasses of the abstract class are again
  specified in italics.

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Dependencies

• A dependency is a using relationship that states
  that a change in a specification of one thing may
  effect another thing that uses it
• You will use dependencies in the context of
  classes to show that one class uses another class
  as an argument in its methods signature.

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Generalization

• A generalization is a relationship between a
  general thing (a superclass) and a more specific
  kind of that thing (a subclass).
• It is a is-a-kind-of relationship.

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Association

• An association represents a relationship that
  specifies that objects of one thing are connected
  to objects of another.

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Aggregation

• An association in which one class represents a
  larger thing, which consists of smaller things is
  called an aggregation relation
• It is a has-a relationship meaning an object of
  the whole has objects of the part.

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Composite

• In a composite aggregation, an object may be a
  part of only one composite at a time. For
  example, a Frame belongs to exactly one Window.
• In simple aggregation, a part may be shared by
  several wholes. For example a Wall may be a part
  of one or more Room objects.

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Realization-Interfaces

• A realization relationship shows that one class
  implements the interface of another class.
• A realization can be represented in two ways.
• Design View (canonical form)
• Systems Implementation View (elided form)

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Realization
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Packages
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Package - Client
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Package - Policies
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Package - GUI