---
title: "Representing dynamic behavior in OOA"
subject: "Object Oriented Analysis and Design"
chapter: 2
key: "semester_6/object_oriented_analysis_and_design:dynamic-behavior-representation-ooa"
source: https://www.bctengineer.com/q/semester_6/object_oriented_analysis_and_design/dynamic-behavior-representation-ooa
site: BCT Engineering
---

# Representing dynamic behavior in OOA

Object Oriented Analysis and Design · Chapter 2: Object Oriented Analysis

- Asked in: 2072 Asoj, 6 marks
- Video: [LECTURE 36 – OOAD –DYNAMIC MODELLING - BCA SEM 6](https://www.youtube.com/watch?v=DeHjfd1nRxQ) — BOSCOCAMPUSVISION
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/object_oriented_analysis_and_design/dynamic-behavior-representation-ooa
- Whole chapter: https://www.bctengineer.com/md/semester_6/object_oriented_analysis_and_design/chapter-2

## Question

How can you represent the dynamic behavior of the system in Object Oriented Analysis (OOA)? Explain with example.

## Short answer

Dynamic behavior is represented with UML behavioral diagrams: use case descriptions, system sequence diagrams (events), collaboration diagrams (messages), state machine diagrams (object lifecycle), activity diagrams (workflow), and operation contracts. For a library, a state diagram shows Book going from Available to Issued to Overdue.

## Answer

**Dynamic behaviour** of a system means how objects interact, how their state changes over time, and how events and flows of control happen when the system runs. In OOA it is represented with UML **behavioural diagrams**, each showing a different aspect.

#### 1. Use case diagram and descriptions
The functional behaviour from the user's point of view: actors and their goals, with a step by step scenario of each use case.

#### 2. System sequence diagram (SSD) and sequence diagram
The events between actor and system (SSD), or the messages among objects in time order.
```text
 Customer         :ATM
    | insertCard()   |
    |--------------->|
    | enterPIN(pin)  |
    |--------------->|
    |<-- accepted ---|
```

#### 3. Collaboration (communication) diagram
The same interaction, drawn by the links among objects, with numbered messages.
```text
 :Customer --1:enterPIN()--> :ATM --2:verify()--> :Bank
```

#### 4. State machine diagram
The life cycle of one object, its states, events and transitions.
```text
 (*)-->[Idle]--insertCard-->[Verify]--ok-->[Active]
          ^                                   |
          +---------- ejectCard --------------+
```

#### 5. Activity diagram
The flow of work with decisions, loops and concurrency (fork, join), also for business processes with swimlanes.

#### 6. Operation contracts
Define the pre-conditions and post-conditions (state changes) of system operations.

**Example: Library book issue** - the *use case* describes the issue steps; the *SSD* shows `issueBook(memberId, bookId)`; the *state diagram* shows `Book` going from `Available` to `Issued` to `Overdue` and back; the *activity diagram* shows the checks (member valid? book free?). Together these models describe how the system behaves in time.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does dynamic behaviour of a system mean?
   A. Its class hierarchy
   B. How objects interact, change state and how control flows over time
   C. Its file structure
   D. Its hardware layout
   Answer: B. Dynamic behaviour covers interaction, state changes over time, events and flows of control. (Key point: Meaning of dynamic behaviour)

2. Which diagram shows the life cycle of a single object with states and transitions?
   A. Use case diagram
   B. Collaboration diagram
   C. State machine diagram
   D. Domain model
   Answer: C. A state machine diagram shows states, events and transitions of one object. (Key point: State machine diagram)

3. What does an activity diagram show that suits business processes?
   A. Class attributes
   B. Package dependencies
   C. Object deployment
   D. Flow of work with decisions, loops, fork/join and swimlanes
   Answer: D. Activity diagrams show workflow with decisions, concurrency and swimlanes. (Key point: Activity diagram features)

4. What do operation contracts define?
   A. Pre-conditions and post-conditions of system operations
   B. Class inheritance
   C. Colour themes
   D. Screen layouts
   Answer: A. Contracts state conditions before and the state changes after a system operation. (Key point: Operation contracts)

5. How does a collaboration (communication) diagram differ in drawing the same interaction as a sequence diagram?
   A. It has no messages
   B. It shows only states
   C. It arranges objects by links and numbers the messages
   D. It shows only actors
   Answer: C. It shows the links among objects with numbered messages instead of a time axis. (Key point: SSD vs collaboration diagram)

## Related in Object Oriented Analysis and Design

- [Object oriented system and core concepts](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Aoo-system-concepts-explained) — Object Oriented Analysis and Design, chapter 1
- [Define object; method implements behavior](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Adefine-object-method-behavior) — Object Oriented Analysis and Design, chapter 1
- [Algorithmic vs object-oriented decomposition](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Aalgorithmic-vs-oo-decomposition) — Object Oriented Analysis and Design, chapter 1
- [Requirement elicitation and system behavior](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Arequirement-elicitation-in-ooa) — Object Oriented Analysis and Design, chapter 2
- [Behavior modeling and four diagrams](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Abehavior-modeling-four-diagrams) — Object Oriented Analysis and Design, chapter 2
- [Short note: Flow of object](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Ashort-note-flow-of-object) — Object Oriented Analysis and Design, chapter 2

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