In ECET 2026 Software Engineering, UML diagrams are frequently tested. Among them, Class Diagrams and Sequence Diagrams are highly important. If you understand the basics and notations, you can easily score marks in SE questions.
⚙️ Concept Notes
1️⃣ UML (Unified Modeling Language)
- A standardized modeling language used to visualize, design, and document software systems.
- Includes structural diagrams (Class, Object, Component, etc.) and behavioral diagrams (Sequence, Activity, State, etc.).
🔹 UML Class Diagram
- Definition: Represents the static structure of a system.
- Shows classes, attributes, methods, and relationships.
- Basic Notation:
- Class: Represented as a rectangle with 3 compartments:
- Class Name
- Attributes
- Methods
- Relationships:
- Association (→ solid line)
- Inheritance (→ solid line with hollow arrow)
- Aggregation (diamond symbol)
- Composition (filled diamond symbol)
- Class: Represented as a rectangle with 3 compartments:
👉 Example: Library Management System
- Classes:
Book,Member,Library - Relationship:
MemberborrowsBook,LibraryhasBooks.
🔹 UML Sequence Diagram
- Definition: Represents dynamic behavior of the system (interaction over time).
- Shows how objects interact through messages.
- Basic Notation:
- Vertical line → Object lifeline
- Horizontal arrow → Message (function call, data transfer)
- Time flows from top to bottom
👉 Example: Online Shopping System
- Objects:
Customer,Website,Payment Gateway,Bank. - Sequence: Customer → Website (Order request) → Payment Gateway → Bank (Validation) → Website (Confirmation).
⚙️ Key Points
- Class Diagram = Structure (What system has?)
- Sequence Diagram = Behavior (How system works over time?)
- Both are essential for designing, analyzing, and understanding software systems.
🔟 10 Expected MCQs – ECET 2026
Q1. UML stands for:
A) Unified Modeling Language
B) Universal Machine Language
C) Unified Machine Learning
D) Universal Modeling Logic
Q2. Class diagram is a:
A) Behavioral Diagram
B) Structural Diagram
C) Deployment Diagram
D) Use-Case Diagram
Q3. Sequence diagram represents:
A) Data flow
B) Object interactions over time
C) File structure
D) Hardware components
Q4. Which symbol in UML shows inheritance?
A) Solid line
B) Dashed line
C) Hollow arrowhead
D) Diamond
Q5. Aggregation is represented by:
A) Hollow diamond
B) Filled diamond
C) Triangle
D) Arrow
Q6. In class diagram, which compartment contains attributes?
A) First
B) Second
C) Third
D) None
Q7. Sequence diagram lifeline is drawn as:
A) Horizontal line
B) Vertical dashed line
C) Arrow
D) Circle
Q8. Which diagram shows “what a system consists of”?
A) Sequence Diagram
B) Class Diagram
C) Activity Diagram
D) State Diagram
Q9. Which diagram shows “how system objects interact over time”?
A) Class Diagram
B) Sequence Diagram
C) Deployment Diagram
D) ER Diagram
Q10. Composition in UML is stronger than:
A) Aggregation
B) Association
C) Generalization
D) Inheritance
✅ Answer Key
| Q.No | Answer |
|---|---|
| Q1 | A |
| Q2 | B |
| Q3 | B |
| Q4 | C |
| Q5 | A |
| Q6 | B |
| Q7 | B |
| Q8 | B |
| Q9 | B |
| Q10 | A |
🧠 Explanations
- Q1 → A: UML = Unified Modeling Language.
- Q2 → B: Class diagram is a structural diagram.
- Q3 → B: Sequence diagram shows interaction over time.
- Q4 → C: Inheritance → solid line with hollow arrowhead.
- Q5 → A: Aggregation → hollow diamond.
- Q6 → B: Attributes are in the second compartment.
- Q7 → B: Lifeline = vertical dashed line.
- Q8 → B: Class diagram shows what the system consists of.
- Q9 → B: Sequence diagram shows dynamic behavior.
- Q10 → A: Composition is a strong form of Aggregation.
🎯 Why This Practice Matters for ECET 2026
- UML diagrams are straightforward theory-based questions in SE.
- Every ECET exam includes at least 2–3 marks from UML (Class, Sequence, Use-case diagrams).
- By practicing notations and examples, you can easily attempt direct questions.
📲 Join Our ECET Prep Community
👉 For daily MCQs, solved notes & video sessions:
Join Telegram @LearnNewThingsHub
