# UNIT 5: Object-Oriented Analysis (OOA) & Design (OOD): OOA Modeling, Data Modeling, OOD Concepts, Class & Object Relationships, Object Modularization, Introduction to UML ## 5.1 Object-Oriented Analysis & Modeling OOA focuses on identifying domain objects, their responsibilities, and relationships from real-world problem statements. ### Key OOAD Principles 1. **Encapsulation**: Bundling attributes and methods into a single class unit while protecting data via private access modifiers. 2. **Abstraction**: Exposing essential contract features while suppressing internal algorithms. 3. **Inheritance**: Subclasses acquire properties and methods of superclasses (`is-a` taxonomy). 4. **Polymorphism**: Ability of a single interface to invoke dynamic method behaviors at runtime. --- ## 5.2 Class & Object Relationships ### 1. Association A general semantic link between two independent classes (e.g., `Student` attends `Course`). Can be Unidirectional or Bidirectional with Multiplicity (`1..1`, `1..*`, `0..*`). --- ### 2. Aggregation A weak `"has-a"` structural relationship where child objects can exist independently of parent object lifecycles. - *Visual Notation*: Line with an **Open (unfilled) Diamond** at parent end. - *Example*: `Department` and `Professor`. Deleting a Department does NOT destroy Professor objects. --- ### 3. Composition A strong `"part-of"` structural relationship where child object lifecycles are bound strictly to parent object lifecycles. - *Visual Notation*: Line with a **Filled (black) Diamond** at parent end. - *Example*: `Building` and `Room`. Deleting a Building automatically destroys all its Rooms. --- ### 4. Generalization / Inheritance An `"is-a"` taxonomy relationship where a specialized subclass inherits attributes and methods from a general superclass. - *Visual Notation*: Line with an **Open Triangular Arrowhead** pointing towards superclass. - *Example*: `Car` is a `Vehicle`. --- ## 5.3 Introduction to Unified Modeling Language (UML) UML is a standardized graphical modeling language developed by Grady Booch, James Rumbaugh, and Ivar Jacobson (Object Management Group - OMG). ### Categorization of UML Diagrams ```text UML Diagrams | +-----------------+-----------------+ | | Structural Diagrams Behavioral Diagrams - Class Diagram - Use Case Diagram - Object Diagram - Sequence Diagram - Component Diagram - Activity Diagram - Deployment Diagram - State Machine Diagram - Package Diagram - Communication Diagram ``` --- ## 5.4 Detailed Breakdown of Key UML Diagrams ### 1. Class Diagram (Structural) Static structural diagram depicting system classes, attributes, operations (methods), access visibility (`+` public, `-` private, `#` protected), and relationships. --- ### 2. Use Case Diagram (Behavioral) Models user functional goals and system scope. - **Actor (Stick Figure)**: External entity interacting with system. - **Use Case (Oval)**: Named sequence of actions delivering measurable value to actor. - **Relationships**: - `<<include>>`: Mandatory sub-use case executed *every time* base use case runs (e.g., `Withdraw Cash` *<<includes>>* `Authenticate PIN`). - `<<extend>>`: Optional/conditional sub-use case executed *only when specific conditions occur* (e.g., `Withdraw Cash` *<<extends>>* `Print Receipt`). --- ### 3. Sequence Diagram (Behavioral / Interaction) Emphasizes **Time Ordering** of messages passed between object lifelines. - **Lifeline (Vertical Dashed Line)**: Represents existence of an object instance over time. - **Activation Box (Rectangle on lifeline)**: Indicates time period during which object is performing an operation. - **Synchronous Message (Solid Arrow head)**: Sender waits for response. - **Asynchronous Message (Half-stick Arrow head)**: Sender does not wait for response. - **Return Message (Dashed Arrow head)**: Returns control/result to caller. --- ### 4. Activity Diagram (Behavioral) Work-flow diagram depicting operational activities, decision branching (`<>`), and parallel concurrency using **Forks** (split 1 flow into parallel flows) and **Joins** (merge parallel flows into 1 flow). --- ### 5. Statechart / State Machine Diagram (Behavioral) Depicts state transitions of a single reactive object in response to discrete events throughout its lifecycle. Includes Initial State (filled circle), Transitions, and Final State (bullseye circle).