INTRODUCTION TO SYSTEM ANALYSIS AND DESIGNPrepared by: L. Fatimah Alageel.Reviwed by: L. Asma Alzaid

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 Course registration system Online order system Online banking system

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:

Investigation of the problem and requirement rather than solution.

System Design: A conceptual solution that fulfills the

requirements, rather than implementation.

System Analyst A business professional who uses

analysis and design techniques to solve business problems using information technology.

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 (SDLC)

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

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 Structure Programming Top-down Programming Structured Design Structured Analysis

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)

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) 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 Can be organized as the fallowing:

1. Structural diagrams: to show the building blocks of your system—features that don’t

change with time. Ex: Class diagram

2. Behavioral diagrams: to show how your system responds to requests or otherwise evolves

over time. Ex: Use case diagram

3. 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 & Collaboration diagram

UML diagrams Another ways of categorizing UML

diagram:

1. Static diagrams to show the static features of the system.

(no change)2. Dynamic diagrams• to show how your system evolves over

time.3. Functional diagrams: • to show the details of behaviors and

algorithms.

3 phase of O-O Approach Object-oriented analysis (OOA) Object-oriented design (OOD) Object-oriented programming (OOP)

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)

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

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Class Diagram Created During OO 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• 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

– Discovery - Invention– What? - How?– Physical - Logical

Example: Analysis vs. Design

figure : Analysis and design versions of a class

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 Programming26

• 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.

Objects27

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.)28

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

Classes29

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

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encapsulation

inheritance

polymorphism

Encapsulation31

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 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)

Inheritance Example

Polymorphism34

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 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.