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Questions and Answers
What is the main purpose of using design patterns in software development?
What is the main purpose of using design patterns in software development?
Which year did Cunningham and Beck conduct their work with Smalltalk regarding design patterns?
Which year did Cunningham and Beck conduct their work with Smalltalk regarding design patterns?
Who are the authors collectively known as the Gang of Four?
Who are the authors collectively known as the Gang of Four?
What is a pattern language in the context of design patterns?
What is a pattern language in the context of design patterns?
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Which of the following is NOT a component of the structure of a design pattern?
Which of the following is NOT a component of the structure of a design pattern?
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How many patterns are included in the Gang of Four’s pattern catalog?
How many patterns are included in the Gang of Four’s pattern catalog?
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What is one key benefit of reusing existing design patterns?
What is one key benefit of reusing existing design patterns?
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Why is prior knowledge of design patterns advantageous for developers?
Why is prior knowledge of design patterns advantageous for developers?
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What is the primary purpose of design patterns in software development?
What is the primary purpose of design patterns in software development?
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How are design patterns similar to recipes in cooking?
How are design patterns similar to recipes in cooking?
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In which scenario are design patterns most useful?
In which scenario are design patterns most useful?
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What distinction is made between beginner and expert developers regarding design patterns?
What distinction is made between beginner and expert developers regarding design patterns?
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How do design patterns contribute to software flexibility?
How do design patterns contribute to software flexibility?
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What is one way design patterns aid in communication among developers?
What is one way design patterns aid in communication among developers?
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Which best describes the nature of design patterns?
Which best describes the nature of design patterns?
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In software design, what common problem does the Dependency Inversion principle aim to solve?
In software design, what common problem does the Dependency Inversion principle aim to solve?
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What do creational patterns primarily focus on?
What do creational patterns primarily focus on?
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Which statement about structural patterns is correct?
Which statement about structural patterns is correct?
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Behavioral patterns are primarily concerned with which aspect?
Behavioral patterns are primarily concerned with which aspect?
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What is a defining characteristic of the Singleton pattern?
What is a defining characteristic of the Singleton pattern?
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Which method is typically used to access the instance of a Singleton class?
Which method is typically used to access the instance of a Singleton class?
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What advantage does lazy creation in a Singleton bring?
What advantage does lazy creation in a Singleton bring?
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Which of the following is NOT a category of design patterns?
Which of the following is NOT a category of design patterns?
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Which pattern deals with decomposing and generalizing the relationship between classes and subclasses?
Which pattern deals with decomposing and generalizing the relationship between classes and subclasses?
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Study Notes
Course Information
- Course title: XBSE2034N SOFTWARE DESIGN
- Instructor: Siti Fazilah
Subject Synopsis
- Software Design: Describes best practices for specific design problems, based on fundamental principles.
- Low-level patterns: Focus on internal software quality attributes.
- High-level patterns: Deal with external software quality attributes.
- Course focus: Applying both software and architectural design patterns, with object-oriented methodology.
Learning Outcomes
- Students will identify and describe software design fundamentals.
- Students will design applications based on specific requirements.
- Students will present designs and justify their adherence to requirements.
Week 1: Introduction to Design Patterns
- Introduces the fundamentals of design patterns in software design.
Software Architectures
- Software architecture provides a fundamental description of a system.
- It details components, meaningful interactions, data flows, and control flows.
Architectural Archetypes
- Software architecture design can be driven by other architectures.
- Reusable microarchitectures on a lower scale are called "design patterns".
Patterns in Architecture
- Discusses the concept of patterns in architecture and how design patterns can inspire software design methods.
Christopher Alexander
- Introduced the concept of pattern languages.
- A pattern language is a set of related patterns that provide a vocabulary for design within a specific context or domain.
- Examples include town patterns (e.g., ring roads, row houses), building patterns (e.g., roof gardens), and construction patterns (e.g., materials, connections).
Typical Software Design Problems
- What design issues can be reused?
- What design vocabulary can be used?
- How can a good design solution be justified?
- How can a design be simplified?
What are Design Patterns?
- A design pattern is a practical and proven solution to a recurring design problem.
- They provide a structured approach to solve common design issues.
- They offer flexibility and reusability across various projects.
Design Patterns: Structure
- Design patterns are reusable templates applicable in various scenarios.
- They evolve over time as classes are reused within systems.
- Component parts include: name, problem description, solution, and consequences (trade-offs/alternatives).
Types of Design Patterns
- Classified into Creational, Structural, and Behavioral categories.
- A list of specific pattern types (e.g., Singleton, Factory) is included.
Experience in Software Design
- Using design patterns is analogous to playing chess.
- Beginners may focus on basic elements, while experts recognize and apply patterns.
- Experience and practice refine design choices.
Design Patterns: Conceptual
- Design patterns are not concrete code; they are conceptual guidelines.
- Used to organize and guide the structure of software.
- Offer a flexible and reusable framework for software development.
Why Use Design Patterns?
- They help developers avoid reinventing solutions to recurring problems.
- They provide a common vocabulary and structure for design discussions.
- Their application is analogous to using a guidebook or an expert's knowledge in solving design problems.
Design Vocabulary
- Design patterns create a shared vocabulary for design discussions.
- Simplify discussions by offering terms that describe design solutions clearly.
- They specify software solutions and clarify the original situation.
- Improved communication between developers is emphasized.
Background: Origin of Design Patterns
- The concept of software design patterns emerged during the 1980s with Smalltalk and GUI development.
- The "Gang of Four" (Gamma, Helm, Johnson, and Vlissides) popularized the concept with their book "Design Patterns: Elements of Reusable Object-Oriented Software."
The Gang of Four
- A group of software engineers recognized for their significant contribution to the field of design patterns.
- They focused notably on creating reusable designs for object-oriented software development.
Why Designers Need Patterns
- Design patterns help promote reuse of the knowledge and experience of many software designers.
- They expedite software construction.
- They create better communication among developers by creating a consistent vocabulary.
Evolution of Design Patterns
- Christopher Alexander's work on architectural patterns laid the foundation for design patterns.
- The "Gang of Four's" Design Patterns book is notable for developing design patterns as a catalog to provide an organized approach for creating reusable object oriented software.
Gang of Four's Pattern Catalogue
- The catalog created, lists the 23 patterns categorized into creational, structural, and behavioral patterns.
- These patterns were grouped according to their purpose to improve developer comprehension.
- The grouping has become a standard organization method.
Pattern Languages
- A pattern language is a collection of related patterns used for a specific software design problem domain.
- Choosing a relevant pattern language depends heavily upon the specific context.
Structure of a Design Pattern
- Typical elements within a design pattern definition
- Pattern name and classification
- Intended purpose and motivation
- Applicability, structure, participants, collaborations, consequences, and implementations
Software Design & Architecture Stack
- Illustrates the relationship between software development concepts ranging from Enterprise Patterns to Programming Paradigms to Clean Code.
- Categorizes methods by area of application, which in turn can provide a context for using specific design patterns.
Categories of Patterns
- Patterns are often classified into creational, structural, and behavioral categories.
- Categorization aids in understanding, and usage from understanding of context.
Classification of GoF Patterns
- A graphical representation listing the 23 patterns in the GoF catalog and grouping them based on their nature (origin, behaviors, structures).
Creational Patterns
- Deal with creating new objects or cloning existing ones.
- Allow flexibility in object creation, without specifying concrete classes.
- This process reduces complex object-creation methods and makes the design more flexible by allowing developers to use their specific implementations for creating objects.
Structural Patterns
- Detail how objects interact and are connected to each other.
- Focus on hierarchical relationships and collaborations in object-oriented designs.
Behavioural Patterns
- Deal with how objects interact and distribute work among themselves.
- Describe how objects can work together to achieve a common goal.
Singleton Pattern
- A creational design pattern that restricts the instantiation of a class to a single object.
- Ensures that only one instance of a class exists in the system.
- This approach simplifies program design by allowing access of the class through a method. A global method of access is typically created to access the single class instance.
Singleton Pattern: Advantages
- Facilitates global access to a class instance.
- Ensures only a single instance exists.
- Promotes reusability and code organization.
- The example provided highlights the key features of a singleton design.
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Description
Explore the fundamentals of design patterns in software design with this quiz. Test your knowledge on low-level and high-level patterns, as well as the principles that guide software architecture. Perfect for students in the XBSE2034N course.
