Agenda

1. Object Diagrams
2. Package Diagrams
3. Component Diagrams
4. Deployment Diagrams

Object Diagrams

Definition

An object diagram shows a snapshot of the system at a particular time — instances of classes and the links between them.

Purpose

• Visualize examples of how objects are related at runtime.

• Understand class diagram structure by concrete examples.

Key Elements

Objects, attribute values, and links.

Example: E-commerce System

Class diagram

Example object diagram

Example: Parties

Interactive Task

Assume we want to model arithmetic expressions with variables:

Expr ::= Const Int | Var String | Plus Expr Expr | Times Expr Expr

Tasks

• Draw a class diagram for the given model

• Draw an object diagram containing at least one instance every class, all connected.

Package Diagrams

Definition

Package diagrams organize elements (classes, components, other packages, …) into groups.

Purpose

Manage large models and clarify dependencies among system parts.

Key Elements

Packages, dependencies, imports, merges.

Structure

• each element is part of a single package
• same package can contain both (sub)packages and other elements

Ways of showing packages on diagrams

Example: E-commerce Application Packages

Package structure for an e-comerce app

Example: Well-structured, clear flow diagram

Example: Package structure for a web service

Interactive Exercise

Task: Given several classes/Packages (Website, Mobile App, Payment, CustomerService, Cart, ProductDB, CustomerDB), propose a modular package structure.

Goal: Reduce coupling and improve clarity.

Component Diagrams

Definition

Describe how software components (subsystems, modules, libraries) are connected.

Purpose

Model large-scale structure and interactions between replaceable parts.

Key Elements

Components, interfaces, ports, dependencies.

Component diagrams: Key takes

Components represent pieces that are independently purchasable and upgradeable

• They are about how customers want to relate to software

• Buy components one piece at a time

• Upgrade one component or another at any time

  • old and new components should work seamlessly

• Mix and match pieces from different providers

Example: Sales server component diagram

Interactive Task

You are given a system for online learning (students, courses, and grading services).

Identify 3–5 major components and describe their provided and required interfaces.

Deployment Diagrams

Definition

Represent the physical deployment of software artifacts on hardware nodes.

Purpose

Model distributed systems and deployment topologies.

Key Elements

Nodes (devices, servers), artifacts (software units), communication links.

Example: Application Deployment

Exercise

Given a system that includes (but is not limited to) a mobile app, a REST API backend, and a cloud database, create a simple deployment diagram.

Wrap-Up

Takeaway: Structural diagrams complement behavioral ones by showing the static “shape” of a system.