CSCI 452 Object Oriented Analysis and Design

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CSCI 452 Object Oriented Analysis and Design

• Class Diagrams

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Class Diagram

• Part of Static Object modeling
• The diagram specifically shows the entities in
  the system along with each entity's internal
  structure and relationships with other entities
  in the system.
• Only types of entities are shown on a class
  diagram
• Example Employee class, not the instance Justin
  Case
• Used to find out details about the system's coded
  classes or soon-to-be-coded classes, along with
  each class's attributes and methods.
• Class diagrams are particularly useful for
  business modeling, too.
• Business analysts can use class diagrams to model
  a business's current assets and resources, such
  as account ledgers, products, or geographic
  hierarchy.

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Design Class Diagram
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Relationships
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Relationships

• association -- a relationship between instances
  of the two classes. In a diagram, an association
  is a link connecting two classes.
• aggregation -- an association in which one class
  belongs to a collection. An aggregation has a
  diamond end pointing to the part containing the
  whole. Order has a collection of OrderDetails.
• generalization -- an inheritance link indicating
  one class is a superclass of the other. A
  generalization has a triangle pointing to the
  superclass. Payment is a superclass of Cash,
  Check, and Credit.
• A navigability arrow on an association shows
  which direction the association can be traversed
  or queried.
• The multiplicity of an association end is the
  number of possible instances of the class
  associated with a single instance of the other end

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Composition and Aggregation

• Aggregation Associations in which an object is
  part of a whole
• Aggregation is denoted by a diamond at the whole
  end
• Composition a strong association in which the
  part can belong to only one whole -- the part
  cannot exist without the whole
• Composition is denoted by a filled diamond at the
  whole end

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Class Information, Visibility, and Scope

• The class notation is a 3-piece rectangle with
  the class name, attributes, and operations
• Static members are underlined. Instance members
  are not
• The operations follow this form
• ltaccess specifiergt ltnamegt ( ltparameter listgt)
  ltreturn typegt
• The parameter list shows each parameter type
  preceded by a colon
• Access specifiers appear in front of each member

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Dependency and Constraints

• A dependency is a relation between two classes in
  which a change in one may force changes in the
  other.
• Dependencies are drawn as dotted lines.
• Co_op depends on Company.
• A constraint is a condition that every
  implementation of the design must satisfy
• Constraints are written in curly braces
• The constraint on our diagram indicates that a
  Section can be part of a CourseSchedule only if
  it is not canceled

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Association Class

• Used to indicate many to many relationships
• Allows to denote an association as a class

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Qualified Association

• Contains a qualifier that is used to select an
  object or objects from a larger set of related
  objects
• Selection is based on a key
• Allows to filter the associations