System Analysis and Design Lecture notes

This lecture note introduces you to the process of building effective information systems.

You will learn:

* How to identify and define user needs
* How to document system requirements clearly
* The steps for designing system structure and functions
* Tools like data flow diagrams, ER diagrams, and use case models
* Methods for testing, implementing, and maintaining systems

You will apply real-world examples to analyze business problems and design practical solutions.

1. Prof. Sadiq Thomas and Mrs LK Tohomdet Air Force Institute of Technology, Kaduna Faculty of Ground & Communication Engineering Information & Communication Technology Department Course Title: Information System Analysis and Design Course Code: 413 No. of Units: 2 Lecturers: Prof. Sadiq Thomas & Mrs. LK Tohomdet Email: [email protected] WEEK TWO

2. Week Two: Course Outline Introduction to Information Systems Analysis and Design (ISAD) Importance of ISAD in developing efficient systems Overview of the System Development Life Cycle (SDLC) Phases of SDLC: Strategy and Planning, Analysis, Design, Implementation, Maintenance OO Systems Analysis Techniques Process Modelling Flow Chart Dataflow Diagram Function Decomposition Diagramming

3. OVERVIEW System analysis delves into the inner workings of an existing system or a proposed one to understand its functionality, limitations, and potential for improvement. Analysts employ various techniques to gather information, model the system, and define its requirements. In this lecture, we'll explore four key techniques:

4. PROCESS MODELLING DEFINATION Process modelling is the systematic representation of a business process or workflow, visually depicting the sequence of steps, actors involved, and decision points. Imagine it as a detailed map or blueprint of how work gets done within an organization. It uses various techniques like: Flowcharts Data Flow Diagrams (DFDs), Function Decomposition Diagrams, and Entity-relationship (ER) diagrams To capture different aspects of the process.

5. Process modelling is an invaluable tool for system analysts, offering several key benefits: Deep Understanding of Existing Systems: Creates a clear visual representation of current operations, enabling analysts to identify: Inefficiencies and bottlenecks that hinder performance. Opportunities for improvement and potential areas for automation. Facilitates communication and collaboration across teams, ensuring everyone has a shared understanding of the process. Design Foundation for New Systems: Serves as a roadmap for designing and developing new systems that are: Aligned with business goals and user needs. Helps prioritize functionalities and features during development. Enhanced Communication and Collaboration: Provides a common language for stakeholders, including analysts, developers, and users, to discuss and understand the system. IMPORTANCE OF PROCESS MODELLING IN SYSTEM ANALYSIS

6. Process modelling is an invaluable tool for system analysts, offering several key benefits: Streamlined Documentation and Training: Offers a readily accessible and understandable documentation of the system, simplifying maintenance and future modifications. Serves as a training tool for new employees, reducing onboarding time and ensuring consistent process execution. Offers an easy-to-use reference point for troubleshooting and problem-solving. Continuous Improvement and Performance Analysis: Enables simulation and analysis of the process, identifying potential problems before they occur. Facilitates performance tracking and measurement, quantifying the impact of changes and improvements. Provides a foundation for continuous process improvement initiatives. IMPORTANCE OF PROCESS MODELLING IN SYSTEM ANALYSIS

7. A flowchart is a type of diagram that represents a workflow or process. A flowchart can also be defined as a diagrammatic representation of an algorithm, a step-by-step approach to solving a task. WHAT IS A FLOWCHART

8. Terminal/Terminator This box is of an oval shape which is used to indicate the start or end of the program. Process This is a rectangular box inside which a programmer writes the main course of action of the algorithm or the main logic of the program. Decision This is a rhombus-shaped box, control statements like if, condition like a > 0, etc are written inside this box. Flow arrow This arrow line represents the flow of the algorithm or process. SYMBOLS

9. Document Represents the generation or modification of a physical or digital document. Data or Input/Output This is a parallelogram-shaped box inside which the inputs or outputs are written Stored Data Represents a location where data is stored and retrieved during the process SYMBOLS

10. Algorithm: Start  Input 2 variables from user Now check the condition If a > b, goto step 4, else goto step 5. Print a is greater, goto step 6 Print b is greater Stop EXAMPLE 1

11. Algorithm: 1. Start 2. Now initialise c = 1 3. Now we check the condition if c < 11, then goto step 4 otherwise goto step 6. 4. Print c 5. c = c + 1 then goto step 3 6. Stop EXAMPLE 2

12. TYPES OF FLOWCHART Three types of flowcharts are listed below: Process flowchart:  This type of flowchart shows all the activities that are involved in making a product. It provides a pathway to analyze the product to be built. A process flowchart is most commonly used in process engineering to illustrate the relation between the major as well as minor components present in the product. It is used in business product modelling to help understand employees about the project requirements and gain some insight into the project.

13. TYPES OF FLOWCHART Data flowchart:  As the name suggests, the data flowchart is used to analyze the data, specifically it helps in analyzing the structural details related to the project. Using this flowchart, one can easily understand the data inflow and outflow from the system. It is most commonly used to manage data or to analyze information to and fro from the system. Business Process Modelling Diagram:  Using this flowchart or diagram, one can analytically represent the business process and help simplify the concepts needed to understand business activities and the flow of information. This flowchart illustrates the business process and models graphically which paves the way for process improvement.

14. Advantages Disadvantages It is the most efficient way of communicating the logic of the system. Flowcharts are challenging to draw for large and complex programs. It acts as a guide for a blueprint during the program design. It does not contain the proper amount of details. It also helps in the debugging process. Flowcharts are very difficult to reproduce. Using flowcharts we can easily analyze the programs. Flowcharts are very difficult to modify. flowcharts are good for documentation. FLOWCHART

15. \ Algorithm: Start Now initialise c = 1 Now check the condition if c < 6, then goto step 4. Otherwise goto step 6 Print 3 * c c += 1. Then goto step 3. Stop QUIZ 1

16. Function decomposition diagramming Function decomposition diagramming DFD LEVEL 0 DATA FLOW DIAGRAM

17. DFD  is the abbreviation for  Data Flow Diagram . The flow of data of a system or a process is represented by DFD. It also gives insight into the inputs and outputs of each entity and the process itself. DFD does not have control flow and no loops or decision rules are present. Specific operations depending on the type of data can be explained by a flowchart. It is a graphical tool, useful for communicating with users ,managers and other personnel. it is useful for analyzing existing as well as proposed system. WHAT IS DFD?

18. DFD rules and tips Each process should have at least one input and an output. Each data store should have at least one data flow in and one data flow out. Data stored in a system must go through a process. All processes in a DFD go to another process or a data store. WHAT IS DFD?

19. SYMBOLS Yourdon and Coad Yourdon and DeMarco External Entity Process Data Store Data Flow

20. A data flow diagram can dive into progressively more detail by using levels and layers, zeroing in on a particular piece.  DFD levels are numbered 0, 1 or 2, and occasionally go to even Level 3 or beyond. DFD LEVELS AND LAYERS

21. DFD Level 0 is also called a Context Diagram. It’s a basic overview of the whole system or process being analyzed or modelled. It’s designed to be an at-a-glance view, showing the system as a single high-level process, with its relationship to external entities. It should be easily understood by a wide audience, including stakeholders, business analysts, data analysts and developers.  DFD LEVEL 0

22. DFD Level 1 provides a more detailed breakout of pieces of the Context Level Diagram. You will highlight the main functions carried out by the system, as you break down the high-level process of the Context Diagram into its subprocesses.  DFD LEVEL 1

23. DFD Level 2 then goes one step deeper into parts of Level 1. It may require more text to reach the necessary level of detail about the system’s functioning. DFD LEVEL 1

24. Advantages Disadvantages It helps us to understand the functioning and the limits of a system. At times DFD can confuse the programmers regarding the system. It is a graphical representation which is very easy to understand as it helps visualize contents. Data Flow Diagram takes long time to be generated, and many times due to this reasons analysts are denied permission to work on it Data Flow Diagram represent detailed and well explained diagram of system components. It is used as the part of system documentation file. DATA FLOW DIAGRAM

25. \ Imagine you're designing a system for a library to manage book borrowing and returning. What are the main entities outside the library system (external entities) and what information does the system exchange with them? How does the library system process this information internally? QUIZ 2

26. Function decomposition diagramming Function decomposition diagramming DFD LEVEL 0 FUNCTION DECOMPOSITION

27. Functional decomposition is a system design and analysis method that involves breaking down a complex system into smaller, more manageable components.  Furthermore, we break down complex systems using specific functions and relationships. It’s a process of breaking down a system into its constituent parts, identifying functions, and defining how they interact to achieve the system’s objectives. The goal of functional decomposition is to simplify complex systems into smaller, more manageable, and understandable parts. Functional decomposition makes it easy to design, analyze , and implement complex systems conveniently. What is Functional Decomposition?

28. The first step is to identify the system’s primary functions.  This process involves defining what the system does and what it is supposed to achieve. The next step is to divide the main functions into smaller sub-functions. Additionally, each main function is broken down into smaller, more manageable parts based on their specific tasks. What is Functional Decomposition?

29. We define the relationships between the sub-functions.  This involves understanding how the sub-functions interact and collaborate to achieve the overall system objectives. We also represent the relationships between sub-functions visually. We typically do it using a  functional block diagram , which shows the different sub-functions and how they interact. We refine the functional decomposition. It involves reviewing the functional block diagram. Additionally, we make necessary modifications to ensure it accurately reflect the system and its functions. What is Functional Decomposition?

30. Example Distance education information system where students can manage and access all the courses online.  Here we divide the distance education information system into four easy-to-manage parts: student management, transcript management, course management, and registration management systems. Additionally, we divide each subsystem further into two parts.

31. Advantages Disadvantages It simplifies complex systems, by breaking down a complex system into smaller, simpler components Time consumption As we break down systems into smaller, modular components, functional decomposition makes it easier to reuse components in future projects. Risk of oversimplification, lack of integration By providing a clear visual representation of the different components and relationships, it improves communication between stakeholders. FUNCTIONAL DECOMPOSITION

32. CONCLUSION