Question 1 of MCS-219: Object Oriented Analysis and Design.
Answer:In Object-Oriented Analysis and Design (OOAD), a system is understood using three complementary models: Object Modeling, Dynamic Modeling, and Functional Modeling. Each focuses on a different aspect of the system.
Object Modeling
Object modeling describes the static structure of a system—what objects exist, their attributes, operations, and relationships.
Purpose
- Identifies system objects (classes)
- Defines relationships such as association, inheritance, and aggregation
- Represents the data structure of the system
Diagram Used: Class Diagram
Class Diagram shows:
- Classes
- Attributes and methods
- Relationships (association, generalization, aggregation, composition)
Example elements:
- Class name
- Data members
- Member functions
Dynamic Modeling
Dynamic modeling represents the behavior of the system over time, showing how objects interact and change state.
Purpose
- Shows object interactions
- Describes control flow and event sequences
- Models system behavior
Diagrams Used:
(a) State Diagram (State Transition Diagram)
- Shows different states of an object
- Transitions between states triggered by events
Example:
Account → Active → Closed
(b) Sequence Diagram
- Shows interaction between objects in a time sequence
- Emphasizes message flow
(c) Activity Diagram
- Represents workflows and control flow
- Similar to flowcharts but object-oriented
Functional Modeling
Functional modeling focuses on what the system does, showing data flow and transformations.
Purpose
- Describes input-output processing
- Shows how data moves through the system
- Independent of implementation details
Diagram Used: Data Flow Diagram (DFD)
DFD shows:
- Processes
- Data stores
- External entities
- Data flows
Levels:
- Context Diagram
- Level-0, Level-1 DFDs
Conclusion
Together, object, dynamic, and functional modeling provide a complete understanding of a system by covering its structure, behavior, and functionality.
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