CP317 Software Engineering - Low-level Design 2

CP317 Software Engineering - Low-level Design (Part 2)

• Course information: CP317 Software Engineering, low-level design, part 2, week 4-2. Instructor: Shaun Gao, Ph.D., P.Eng.

Agenda

• Review of week 4-1 topics
• Introduction to procedural-oriented design
• Introduction to object-oriented design
  • Abstraction
  • Inheritance
  • Polymorphism
  • Encapsulation
• Comparison of procedural-oriented design vs. object-oriented design
• Summary

Review of Week 4-1 Topics

• Low-level (detailed) design concepts
• Key tasks in detailed design: understanding requirements, architecture, and systems
• Detailed design creation: interface design (internal/external), shared memory, inter-process communication (IPC)
• Graphical User Interface (GUI) design
• ASCII table use
• Internal component design: structural & behavioral aspects
• Data design and data structure design for detailed design
• Documentation and evaluation of detailed design

Introduction to Procedural-Oriented Design

• Primary focus: functions
• Step-by-step approach that guides applications through instruction sequences
• Instructions executed in a specific order
• Data structure: global and local data
• Diagram shows the flow of control within a procedural-oriented program

Procedural-Oriented Design Disadvantages

• Data protection: data is not protected from unwanted access
• Modification issues: adding new data requires modifying all functions accessing it
• Modeling real world problems: less effective at representing real-world issues
• Complexity & Scalability: becomes problematic when size/complexity increase; difficulties with modification/extension → lacks scalability
• Vulnerability: easier to break (vulnerable) due to lack of proper structure

Introduction to Object-Oriented Design

• Classes: units defining objects (with properties/methods)
• Constructor: special method initializing objects (a class usually has default constructor)
• Destructor: special method automatically called when objects are destroyed (a class usually has default destructor)
• Attributes: properties of a class (things that can be measured or observed)

Object-Oriented Design (cont.)

• Objects: created from classes via constructors (matched parameter types)
• Relationship: between classes and objects

Object-Oriented Design (cont.)

• History of Object-oriented design: data -> methods
• Object orientation combines data & methods into classes (cohesive wholes)
• Object-Oriented Design (OOD): A process of designing interacting objects for software problem-solving
• Comparison: Procedural-oriented design vs. Object-oriented design

Object-Oriented Design (cont.)

• Features: Abstraction, Inheritance, Polymorphism, Encapsulation
• Benefits: code reusability (new objects from old), code modularity (object-based), easier maintenance, design stability

Abstraction

• Hiding unnecessary details and showing essential object features
• No implementation details, just the concept
• Benefits: reduced complexity and improved maintainability
• Examples: abstract classes (declaring pure virtual member function in C++)

Inheritance

• Mechanism for derived classes to acquire properties from a base class
• Benefits: increased productivity through code reuse and easier maintenance

Polymorphism

• Method naming consistency across various object data types (or class)
• Polymorphism enables different behaviours depending on specific data types
• Benefits: Code reuse and improved flexibility
• Support different types of function calls

Compile Time Polymorphism (Static Binding)

• Binding is done during compile time
• In C++, non-virtual functions are bound during compile time

Run Time Polymorphism (Dynamic Binding)

• Binding occurs during runtime
• C++ uses virtual functions for run-time polymorphism

Overloading

• Technique allowing functions with the same name but different parameters for different behaviours within a class
• Why Overloading is needed: allows greater flexibility in handling various data types or input sequences
• Examples of Function Overloading

Overriding

• Function definition in a subclass that matches a method defined in a superclass
• Method overrides offer custom implementation
• Examples of Function Overriding

Encapsulation

• Hiding internal object characteristics and functionality (prevent outside modifications; users only see appropriate interfaces through public methods)
• Benefits: improved software reliability, easier maintenance, reusability
• Examples: setter(...) and getter() methods for accessing data elements inside an object

Abstraction vs. Encapsulation

• Abstraction: implementation hiding via abstract classes/interfaces
• Encapsulation: data hiding via access modifiers (public, private, protected)

POD vs. OOD

• Procedural vs. Object-Oriented Programming
• Procedural Programming
  • Global data
  • General function
  • Local data (variables)
• Object-Oriented Programming
  • Objects
  • Properties
  • Methods
  • Objects

POD vs. OOD (Advantages/Disadvantages)

• Procedural Programming (Advantages): code reusability, program flow tracking, module construction
• Procedural Programming (Disadvantages): global data vulnerability, complex data verification, difficult real-world modelling
• Object-Oriented Programming (Advantages): task partitioning (in projects), secure programs (using data hiding), object categorizing/mapping, flexible code upgrade/enhancement through inheritance, eliminate redundant code, greater modularity, data abstraction enhances reliability, flexible dynamic binding
• Object-Oriented Programming (Disadvantages): more resources required, complex behaviour & debugging, tight coupling in inheritance, message passing affects reusability

Think-Pair-Share

• Group projects: which OOP features can be utilized

Summary

• Procedural-oriented design
• Object-oriented design
• Abstraction (concept)
• Inheritance (concept)
• Polymorphism (concept)
• Encapsulation (concept)
• Differences between POD and OOD

Announcement

• Group formation deadline
• Test 1 details (60 min, cover week 1-4 material), upcoming date, location (LH3094). Students need their laptops.