Object Diagram and Class Diagram Relationship Quiz

Object Diagram and Class Diagram

• Object diagram shows instances that are compatible with a given class diagram.
• Generalization and Specialization are hierarchic in nature, with more general (superclasses) and more specialized (subclasses) categories.

Generalization and Specialization

• Generalization abstracts out more general bits of description from specialized classes.
• Specialization involves inheriting common attributes, relationships, and operations from superclasses.
• Subclass and superclass are similar to subtype and supertype in EER (Entity-Relationship Diagram).

Database Modeling

• Complete, disjoint specialization: one table for each subclass, containing all attributes from the superclass.
• Incomplete, overlapping specialization: two tables, one for the superclass and one for the subclasses, with NULL values for unused attributes.
• Incomplete, disjoint specialization: one table for each class, with a 0..1 to 1 relationship between subclasses and superclasses.

Package Diagram

• A package diagram groups classes, components, and subsystems, with relationships between them.
• Packages can have relationships and can be used to create a structure (architecture) for large systems.
• Package diagrams allow for parallel development of systems.

State Diagram

• A state diagram describes the states an object can be in, the events that trigger state changes, and the actions performed during these events.
• States are all the allowed combinations of attribute values.
• State diagrams are often used for technical objects, such as bank machines or garage doors.

Class and Instance

• A class is a description of a set of objects with similar attributes, operations, methods, relationships, and semantics.
• The purpose of a class is to declare a collection of methods, operations, and attributes that fully describe the structure and behavior of objects.
• An object is an instance that originates from a class, structured and behaving according to its class.

Object

• An object is a thing with a well-defined role in the application domain, with state, behavior, and identity.
• Objects can be tangible (person, place), concepts or events (department, registration), or IT artifacts (user interface, controller, scheduler).
• Objects exhibit behavior as well as attributes, different from entities.