Lesson 9

1. Architectural Design

Definition: Architectural design is the process of defining a structured solution that meets all
technical and operational requirements while optimizing quality attributes such as performance,
security, and manageability.

• Purpose: Establishes the high-level structure of a software system, ensuring that it

satisfies the system’s requirements and constraints.

• Core Elements:

o Components: Major elements of the system (e.g., modules, functions).

o Connectors: Mechanisms for communication (e.g., APIs, network protocols).

o Configuration: The layout of components and connectors within the system.

• Architectural Patterns:
o Layered Architecture: Separates concerns by defining layers (e.g., presentation,
business logic, data).
o Client-Server Architecture: Splits functionality between service providers
(servers) and requesters (clients).
o Microservices Architecture: Decomposes applications into small, independently
deployable services.

o Event-Driven Architecture: Uses events to trigger and communicate between

components.

Benefits:
• Facilitates scalability and flexibility.

• Enables easier maintenance and system evolution.

• Supports separation of concerns, enhancing modularity.

2. Distributed Systems Architectures

Definition: Distributed systems architecture involves designing systems where components

located on networked computers communicate and coordinate actions by passing messages.

• Characteristics:
o Decentralization: No single point of control; components operate independently.
 o Scalability: Supports expansion by adding new nodes or services.

o Fault Tolerance: Can continue operation despite individual component failures.

• Common Architectures:

o Client-Server: Clients request services provided by central servers.

o Peer-to-Peer (P2P): Each node acts as both client and server, sharing resources
directly.

o Service-Oriented Architecture (SOA): Services are shared and reused across

distributed systems, often implemented with web services or RESTful APIs.

o Cloud-Based Architecture: Leverages cloud services to manage infrastructure,

scaling, and load balancing.

Challenges:

• Concurrency: Managing multiple requests simultaneously.

• Latency and Bandwidth: Network communication can be slow or unreliable.

• Security: Ensuring data integrity, confidentiality, and access control across distributed
components.

3. Object-Oriented Design (OOD)

Definition: Object-oriented design focuses on defining a system as a collection of interacting

objects, each representing an entity with attributes and behaviors.

• Core Concepts:

o Classes and Objects: A class defines the structure and behaviors; objects are
instances of classes.

o Encapsulation: Protects object state by hiding internal details.

o Inheritance: Allows new classes to inherit characteristics from existing ones.

o Polymorphism: Enables a single function to handle different data types.

• Design Principles:
o SOLID Principles: Guide good OO design (Single Responsibility, Open-Closed,
Liskov Substitution, Interface Segregation, Dependency Inversion).
o Design Patterns: Reusable solutions for common problems (e.g., Factory,
Singleton, Observer).
Benefits:

• Promotes modularity and reusability.

• Enhances maintainability by allowing easier updates.

• Supports a natural mapping to real-world entities.

4. Real-Time Software Design

Definition: Real-time software design is focused on systems that must operate within strict
timing constraints, where correctness depends on timely execution.

• Types of Real-Time Systems:

o Hard Real-Time: Missing a deadline could lead to catastrophic failure (e.g.,
medical devices).

o Soft Real-Time: Missing a deadline may degrade performance but is tolerable

(e.g., video streaming).

• Key Concepts:

o Deterministic Execution: Predictable timing for responses to inputs.

o Scheduling Algorithms: Ensure that tasks meet timing constraints (e.g., Rate
Monotonic, Earliest Deadline First).

o Concurrency Control: Manages access to shared resources without blocking

critical operations.

Challenges:

• Balancing resource usage with timing constraints.

• Designing for robustness in unpredictable environments.

• Testing for all potential timing scenarios.

5. Design with Re-use

Definition: Design with re-use emphasizes using existing components, frameworks, or modules
to build new systems, reducing development time and cost.

• Types of Re-usable Assets:

o Code Libraries: Ready-to-use code blocks that handle common functionality.
 o Frameworks: Provide a structured environment with reusable components (e.g.,
Spring for Java, Django for Python).

o Design Patterns: General solutions to recurring design problems.

o APIs and Services: Third-party services that can be integrated (e.g., payment
gateways, data analytics services).

Approaches:

• Component-Based Development: Develops software by assembling reusable

components.

• Service-Oriented Architecture (SOA): Focuses on creating modular services that can be

reused across applications.
Benefits:

• Reduces development time by avoiding redundant coding.

• Improves reliability by using well-tested components.

• Enhances flexibility, as components can be swapped or upgraded.

6. User Interface Design

Definition: User interface (UI) design involves creating the visual and interactive elements of
software that allow users to engage with the system.

• Core Principles:

o Usability: Ensures ease of use and intuitive navigation.

o Consistency: Similar elements should look and behave similarly across the
application.

o Feedback: Provides users with timely responses to their actions.

o Affordance: Design cues that suggest how elements should be used (e.g.,
clickable buttons).

• UI Design Process:

o User Research: Understand the target audience and their needs.

o Wireframing and Prototyping: Create low- and high-fidelity sketches of the UI.
o Testing and Iteration: Refine the design based on user feedback.
Common Patterns:

• Navigation Bars and Menus: Provide easy access to different parts of the application.

• Forms and Input Fields: Allow users to submit information.

• Icons and Buttons: Offer recognizable and actionable elements for users.
Benefits:

• Improves user satisfaction and engagement.

• Increases productivity by streamlining user interactions.

• Reduces errors and the learning curve for new users.