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Introduction To System Analysis and design

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1 Introduction To System Analysis and design
Prepared by: L. Fatimah Alageel. Reviwed by: L. Asma Alzaid

2 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.

3 Examples of Information Systems
Course registration system Online order system Online banking system

4 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.

5 System Analysis vs. System Design
Investigation of the problem and requirement rather than solution. System Design: A conceptual solution that fulfills the requirements, rather than implementation.

6 System Analyst A business professional who uses analysis and design techniques to solve business problems using information technology.

7 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.

8 Traditional System Development Life Cycle (SDLC)

9 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

10 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

11 Structured System Development
Structure Programming Top-down Programming Structured Design Structured Analysis

12 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

13 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.

14 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).

15 UML diagrams 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 & Collaboration diagram

16 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.

17 3 phase of O-O Approach Object-oriented analysis (OOA)
Object-oriented design (OOD) Object-oriented programming (OOP)

18 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

19 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

20 Class Diagram Created During OO Analysis

21 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

22 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.

23 Analysis vs. Design Discovery - Invention What? - How?
Physical Logical

24 Example: Analysis vs. Design
figure : Analysis and design versions of a class

25 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, …)

26 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.

27 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)

28 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

29 Classes objects sharing common characteristics
dictate the behavior of the object contain state: attributes, fields, variables, data member behavior: functions, methods, function member

30 3 Pillars of Object-Orientation
encapsulation inheritance polymorphism

31 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

32 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)

33 Inheritance Example

34 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) .

35 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.

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