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Introduction To System Analysis and design. Prepared by: L. Fatimah Alageel . Reviwed by: L. Asma Alzaid. What Is An Information System?.

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introduction to system analysis and design

Introduction To System Analysis and design

Prepared by: L. Fatimah Alageel.

Reviwed by: L. AsmaAlzaid

what is an information system
What Is An Information System?
  • An information system is a collection of interrelated components that collect, process, store, and provide as output the information needed to complete a business task.
examples of information systems
Examples of Information Systems
  • Course registration system
  • Online order system
  • Online banking system
what is system analysis about
What Is System Analysis About?
  • Understanding the goals and strategies of the business.
  • Defining the information requirements that support those goals and strategies.
  • It is not about programming.
system analysis vs system design
System Analysis vs. System Design
  • System Analysis:
    • Investigation of the problem and requirement rather than solution.
  • System Design:
    • A conceptual solution that fulfills the requirements, rather than implementation.
system analyst
System Analyst
  • A business professional who uses analysis and design techniques to solve business problems using information technology.
the role of a system analyst
The Role of a System Analyst
  • Investigate, analyze, design, develop, installs, evaluate, and maintains a company’s information systems.
  • Business knowledge.
  • Business problem solver.
  • Help translate business requirements into IT projects.
traditional system development life cycle sdlc1
Traditional System Development life Cycle (SDLC)
  • Project planning– initiate, ensure feasibility, plan schedule, obtain approval for project
  • Analysis– understand business needs and processing requirements
  • Design– define solution system based on requirements and analysis decisions
  • Implementation– construct, test, train users, and install new system
  • Support– keep system running and improve
two approaches to system development
Two Approaches to System Development
  • Traditional (Structured) approach
    • Also called structured system development
    • Structured analysis and design technique (SADT)
    • Includes information engineering (IE)
  • Object-oriented approach
    • Also called OOA, OOD, and OOP
    • Views information system as collection of interacting objects that work together to accomplish tasks
structured system development
Structured System Development
  • Structure Programming
  • Top-down Programming
  • Structured Design
  • Structured Analysis
object oriented approach
Object-Oriented Approach
  • Completely different approach to information systems
  • Views information system as collection of interacting objects that work together to accomplish tasks
    • Objects– things in computer system that can respond to messages
    • Conceptually, no processes, programs, data entities, or files are defined – just objects
  • OO languages: Java, C++, C# .NET, VB .NET
object oriented analysis and design ooad
Object-oriented Analysis and design (OOAD)
  • OOAD essential for creating well-designed,

& maintainable software system

  • All Software Analysis and Design is preceded by the analysis of requirements.
  • analysis models the “real-world” requirements, independent of the implementation environment.
  • design applies object-oriented concepts to develop and communicate the architecture and details of how to meet requirements.
unified modeling language uml
Unified Modeling Language (UML)
  • UML (Unified Modeling Language) is a graphical language that is suit-able to express software or system requirements, architecture, and design.
  • UML used for both database and software modeling
  • UML modeling also supports multiple views of the same system.
    • use case diagram shows the purposes of the system (use cases) and the users (actors).
uml diagrams
UMLdiagrams
  • Can be organized as the fallowing:
    • Structural diagrams:
      • to show the building blocks of your system—features that don’t change with time.
      • Ex: Class diagram
    • Behavioral diagrams:
      • to show how your system responds to requests or otherwise evolves over time.
      • Ex: Use case diagram
    • Interaction diagrams:
      • Is a type of behavioral diagram.
      • To depict the exchange of messages within a collaboration (a group of cooperating objects).
      • Ex: Sequence diagram & Collaborationdiagram
uml diagrams1
UML diagrams
  • Another ways of categorizing UML diagram:
    • Static diagrams
      • to show the static features of the system. (no change)
    • Dynamic diagrams
      • to show how your system evolves over time.
    • Functional diagrams:
      • to show the details of behaviors and algorithms.
3 phase of o o approach
3 phase of O-O Approach
  • Object-oriented analysis (OOA)
  • Object-oriented design (OOD)
  • Object-oriented programming (OOP)
object oriented analysis ooa
Object-oriented analysis (OOA)
  • Trying to figure out what the users and customers of a software effort want the System to do.
  • Builds a “real-world” model from requirements
    • client interviews, domain knowledge, real-world experience collected in use cases and other simple notations
  • OOA models address three aspects of the system (its objects)
    • class structure and relationships
    • sequencing of interactions and events
    • data transformations and computations
models of object oriented analysis uml
Models of Object-Oriented Analysis (UML)
  • Structural Model (Data-Oriented)
    • static features
    • what objects are in the system?
    • how are they related?
  • Dynamic Model (Action-Oriented)
    • behavioral aspects
    • what events occur in the system
    • when do they occur and in what order?
  • Functional Model (Both Data and Actions)
    • data transformations
    • “what” does the system do
ex use case analysis
Ex: Use Case (Analysis)
  • Start from requirements
  • Describe response of system to events
    • Normal flow of action
    • Error and exception handling
  • Can implement tests to check use cases
ood object oriented design
OOD: Object Oriented Design
  • Emphasizes a conceptual solution that fulfils the requirements specified in the analysis.
  • Need to define software objects and how they collaborate to fulfill the requirements.
  • For example, in the Library Information System, a Book object may have a title attribute and a display() method.
  • Designs are implemented in a programming language.
  • In the example, we will have a Book class in Java.
analysis vs design
Analysis vs. Design
  • Discovery - Invention
  • What? - How?
  • Physical - Logical
example analysis vs design
Example: Analysis vs. Design

figure : Analysis and design versions of a class

object oriented programming oop
Object-oriented programming (OOP)
  • Writing statements in programming language to define what each type of object does
  • OO Programming Language (e.g. C++, Java,

smalltalk, …)

oop object oriented programming
OOP: Object-Oriented Programming
  • During Implementation, or Object-Oriented Programming, design objects are implemented, such as a book class in Java.
  • Implementation is also known as Coding or Construction.
objects
Objects
  • Concepts, concrete or abstract, with meaning derived from the problem domain “the real world”
  • Provide a basis for implementation.
  • Encapsulation of state (data values) and behavior (operations)
objects cont
Objects (cont.)
  • Exhibit behavior by invoking a method in response to a message.
  • Instances of classes.
  • an object-oriented program is a collection of autonomous interacting and collaborating objects
classes
Classes
  • objects sharing common characteristics
  • dictate the behavior of the object
  • contain
    • state: attributes, fields, variables, data member
    • behavior: functions, methods, function member
3 pillars of object orientation
3 Pillars of Object-Orientation
  • encapsulation
  • inheritance
  • polymorphism
encapsulation
Encapsulation
  • combination of state and behavior
  • implementation details are hidden internally
  • internal mechanisms can change while public interfaces remain stable
  • state may be retrieved using public methods
  • behavior consists of methods activated by receipt of messages
inheritance
Inheritance
  • Classes with similar attributes and operations may be organized hierarchically
  • Common attributes and operations are factored out and assigned to a broad superclass (generalization)
    • generalization is the “is-a” relationship
    • superclasses are ancestors, subclasses are descendants.
  • Classes iteratively refined into subclasses that inherit the attributes and operations of the superclass (specialization)
polymorphism
Polymorphism
  • Polymorphism means same operation may behave differently on different classes.
  • Some Polymorphism types:
    • Overloading: Method with same name but with different arguments (compile-time polymorphism).
    • Overriding: when child class declares a method that has the same type arguments as a method declared by one of its superclass (run-time polymorphism) .
summary
Summary
  • What is information system.
  • System analysis.
  • System analysis vs. system design
  • System development life cycle (SDLC)
  • Unified Modeling Language (UML)
  • Phases of OO Approach.
  • Pillars of OO.