5. Design concepts
Design
process creates
a detailed plan, or blueprint, for a software system based on requirements,
transforming abstract needs into a structured solution before coding
begins. Key steps include understanding requirements, designing the architecture,
creating detailed designs for components, and prototyping/testing to refine the plan. This process
involves breaking down the system into manageable components, defining their
interfaces and interactions, and considering factors like security,
scalability, and user experience to ensure a functional, efficient, and
maintainable product.
The
evolution of software design started with
machine-level instructions in the pioneering days, moved to high-level
languages and object-oriented programming, and then progressed to
client-server, web-based.
Software design concepts
include Abstraction, focusing on essential details; Modularity,
breaking the system into independent units; Information Hiding, protecting
data within modules; Patterns, providing reusable
solutions; Architecture, defining the system's overall structure; and
Functional Independence, which relates to high cohesion and low coupling,
ensuring modules have clear, single responsibilities with minimal dependencies.
Software Quality Attributes
These are the essential characteristics
that describe how well a software product performs and meets user needs.
- Functionality- The
software's capacity to provide functions that meet stated and implied
needs.
- Reliability- The
ability of the software to perform its required functions under stated
conditions for a specified period.
- Usability-The
ease with which users can understand, learns, and operates the software to
achieve their goals effectively.
- Maintainability-The
ease with which the software can be modified, corrected, or enhanced to
fix bugs or add new features.
- Performance
Efficiency-How well the software performs
its functions in terms of resource usage, such as time and memory.
- Security-The
software's ability to protect data and information from unauthorized
access, use, disclosure, alteration, or destruction.
- Portability-The
ease with which software can be transferred from one hardware or operating
environment to another.
- Compatibility-The
ability of the software to operate with other systems, software, or
hardware in a shared environment.
Software
Design has evolved from manual, machine-level
coding in the 1940s to high-level languages, object-oriented programming, and
component-based approaches. Software design is a conceptual blueprint
for constructing a software system, transforming user requirements into a
detailed how-to plan for programmers to implement.
Key Aspects of Software Design
- Requirements
to Solution:
Software design is
the crucial step in the Software Development Life Cycle (SDLC) that bridges the
gap between user requirements (what the system should do) and the actual
implementation (how it will do it).
- Blueprint
for Implementation:
It creates a
detailed plan, similar to architectural blueprints for a building, outlining
the system's structure, modules, interfaces, and data flows.
- Decomposition:
The process breaks
down a large, complex system into smaller, more manageable modules or components,
which make the system easier to understand, develop, and maintain.
- Focus
on How:
While a
requirements document specifies what the system needs to do, the design focuses
on how the system will perform its functions.
Design
Concepts
·
Abstraction: Simplifying
complex systems by focusing on essential features and ignoring irrelevant
details.
·
Architecture-the high-level design of a software system
that defines its fundamental structures, components, and their interactions
· Pattern-It is a
general, reusable solution to a commonly occurring problem in software design
·
Modularity-Dividing
a system into distinct, independent, and interchangeable components
(modules).
·
Information Hiding-Concealing
the internal details of a module, so that only necessary information is
exposed, and preventing access by other modules that don't need it.
·
Refinement- The
process of elaborating a high-level design into more detailed
specifications.
· Design
Patterns- Proven,
reusable solutions to commonly occurring problems in software design.
·
Separation of Concerns
(SoC)- is a design principle in software
engineering that divides a system into distinct, independent sections,
with each part addressing a specific and separate concern. A concern represents
a specific aspect of functionality, such as the user interface, business logic,
or data storage. The ultimate goal is to reduce complexity, improve
maintainability, and increase scalability.
Benefits
of Separation of Concerns
Improved
Organization and Clarity-Code becomes easier to
understand and manage when distinct parts handle different
responsibilities.
Easier
Maintenance-Changes to one concern (e.g.,
updating the UI) are less likely to cause issues in unrelated areas of the
application.
Enhanced
Reusability-Components built with a clear focus
can be reused in other parts of the system or in different projects.
Increased
Flexibility-It becomes simpler to adapt to new
requirements or replace components, such as switching from a web interface to a
console application.
Modularity
in software engineering is the design principle of dividing a complex
system into smaller, independent, and interchangeable units called modules,
each handling a specific function. Breaking down a software system into
smaller, independent parts called modules.
Information
hiding is a software engineering principle
where modules conceal internal design decisions and implementation details from
the rest of the system, exposing only a stable interface for interaction.
Abstraction-Hiding complex
implementation details and exposing only necessary interfaces, allowing modules
to interact without knowing the internal workings.
Information
Hiding-Encapsulating a module's data and
operations to protect it from external access and modification.
Cohesion-The
degree to which the elements within a module are related to and focused on a
single task. High cohesion means a module does one thing well.
Coupling-The
degree of interdependence between different modules. Low coupling is the
goal, meaning modules have minimal dependencies on each other.
Functional
independence in software engineering
means designing software modules so that each module performs a single,
specific task with minimal interaction with other modules. This leads to
high cohesion (elements within a module are strongly related and focused on a
single function) and low coupling (modules are not overly dependent on each
other).
Refinement
is the iterative process of progressively detailing and elaborating on a
system or its components, moving from abstract, high-level concepts to
concrete, low-level implementations It involves breaking down complex tasks
into smaller, more manageable sub-steps and improving the quality of
existing software through ongoing iterations and analysis.
Aspects
in software engineering refer to key considerations throughout the software
development lifecycle, including requirements analysis, design,
development, testing, deployment, and maintenance. They can also refer to
a software characteristic such as functionality, reliability, and portability,
or to cross-cutting concerns like security and performance, which are addressed
by Aspect-Oriented Programming (AOP) techniques.
Refactoring
in software engineering is the
disciplined process of restructuring existing computer code by changing its
internal structure without altering its external behavior or
functionality. The primary goals are to improve code readability,
maintainability, and design, making the software easier to understand, update,
and extend over time.
Object-Oriented
Design (OOD) is a software engineering
methodology that structures a system around objects, which are self-contained
entities representing real-world things with attributes (data) and behaviors
(methods). This paradigm involves defining classes as blueprints for
objects, establishing relationships between them, and using principles
like encapsulation, inheritance, and polymorphism to
create modular, reusable, and adaptable software systems.
Designing
classes involves creating the blueprints for
a system's components, including their attributes, methods, and relationships,
to translate analysis requirements into a concrete implementation plan.
Dependency
inversion is a principle where high-level and
low-level modules both depend on abstractions (like interfaces or abstract
classes), rather than the high-level module directly depending on the low-level
concrete implementation.
Design
for test (or testability) in software engineering
is the practice of creating software with built-in features and structures
that make it easier, more efficient, and more thorough to test throughout the
development lifecycle.
A
design model in software engineering is a
diagrammatic representation of a software system that details its architecture,
data structures, user interfaces, and components, serving as a blueprint for
development.
Data
design element focuses on structuring,
organizing, and representing the data that a system will use, store, and
process. Key data design elements include data objects, data structures,
databases, and data models, which are refined into implementation-specific
formats like ERDs and data dictionaries to manage data
effectively and serve as a blueprint for the software's data architecture.
Assignment 5
1)What is Design Process?
2)Define The followings
1)Abstraction
2) Information Hiding
3) Modularity
4) Refinement
5) Refactoring
6)Aspects
3)What is Design Model?
4)Explain design Elements?
5) What is Functional independence?
6) What is Object-Oriented Design (OOD)?
7) Explain Separation of Concerns (SoC)
8) What is Dependency inversion?
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