Structured system analysis

1. Structured System Analysis Modeling System Function Data Flow Diagram System Flowchart Modeling Stored Data Entity-Relationship Data Dictionary

2. Structured Analysis Throughout the phases of analysis and design, the analyst should proceed step by step, obtaining feedback from users and analyzing the design for omissions and errors . Moving too quickly to the next phase may require the analyst to rework portions of the design that were produced earlier.

3. Structured Analysis They Structured a project into small, well-defines activities and specify the sequence and interaction of these activities. They use diagrammatic and other modeling techniques to give a more precise (structured) definition that is understandable by both users and developers.

4. Structured analysis provides a clear requirements statements that everyone can understand and is a firm foundation for subsequent design and implementation . Part of the problem with systems analysts just asking ‘ the right questions ’ that it is often difficult for a technical person to describe the system concepts back to the user can understand . Structured Analysis

5. Structured methods generally include the use of easily understood, non technical diagrammatic techniques . It is important that these diagram do not contain computer jargon and technical detail that the user wont understand – and does not need understand. Structured Analysis

6. Why do we use these tools? •Use graphics whenever possible to help communicate better with the user . •Differentiate between logical and physical system •Build a logical system model to familiarize the user with system characteristics and interrelationships before implementation. Structured Analysis

7. Modeling System Function Data Flow Diagram (DFD) System Flowchart

8. Data Flow Diagram A Data Flow Diagram (DFD) is a graphical representation of the "flow" of data through an information system. It differs from the system flowchart as it shows the flow of data through processes instead of computer hardware. Data flow diagrams were invented by  Larry Constantine, developer of structured design, based on Martin and Estrin's " data flow graph " model of computation.

9. Data Flow Diagram It is common practice to draw a  System Context Diagram  first which shows the interaction between the system and outside entities. The DFD is designed to show how a system is divided into smaller portions and to highlight the flow of data between those parts. This context-level Data flow diagram is then "exploded" to show more detail of the system being modeled.

10. PASSENGER AIRLINE RESERVATION SYSTEM AIRLINE TRAVEL AGENT Travel Request Preference and Available Flights Ticketing Information Passenger Reservation Context – level flow diagram for an airline reservation system

11. System Flowchart A concrete, physical model that documents, in an easily visualized, graphical form, the system’s discrete physical components (its programs, procedures, files, reports, screens, etc.).

12. System Flowchart A system flowchart is a valuable presentation aid because it shows how the system’s major components fit together and interact . In effect, it serves as a system roadmap. During the information gathering stage, a system flowchart is an excellent tool for summarizing a great deal of technical information about the existing system . A system flowchart can also be used to map a hardware system.

13. System Flowchart System flowcharts are valuable as project planning and project management aids . Using the system flowchart as a guide, discrete units of work ( such as writing a program or installing a new printer ) can be identified, cost estimated, and scheduled. On large projects, the components suggest how the work might be divided into subsystems .

14. Flowcharting Symbols and Conventions

15. Sample Flowchart using predefined process

16. Sample Flowchart showing the predefined process

17. Shows one physical alternative for implementing an inventory system . At the top left, a  Sales receipt  is prepared as output from the   Sell appliance  predefined process. The data from the  Sales receipt   are then input to the  Inventory program . Subsequently, a printed  Cash flow   report goes to the  Financial system .

18. Below the symbols that represent the system files are procedures to send advertising to customers, perform a physical inventory, process incoming shipments from suppliers , and reorder stock . Except for the predefined processes, each symbol represents one of the system’s discrete components at a black-box level.

19. Predefined process —On a system flowchart, a high-level process that is more fully documented in a separate, lower-level flowchart. System flowchart —A tool for documenting a physical system in which each component is represented by a symbol that visually suggests its function.

20. Modeling Stored Data Entity-Relationship Diagram Data Dictionary

21. Entity-Relationship Diagram An entity-relationship model is a systematic way of describing and defining a business process. The process is modeled as components (entities) that are linked with each other by  relationships  that express the dependencies and requirements between them , such as:  one building may be divided into zero or more apartments, but one apartment can only be located in one building .   Entities may have various properties ( attributes ) that characterize them . Diagrams created to represent these entities, attributes, and relationships graphically are called entity–relationship diagrams .

22. Entity-Relationship Diagram The elements that make up an organizational system can be referred to as entities. An Entity may be a person, a place, or a thing, such as a passenger on an airplane, a destination, or a plane . Alternatively that entity may be an event , such as the end of the month , a sales period , or a machine breakdown . A relationship is the association that describes the interaction among entities.

23. Entity-Relationship Diagram EMPLOYEE PHONE EXTENSION is listed for is assigned to One EMPLOYEE is assigned to one PHONE EXTENSION One PHONE EXTENSION is listed for one EMPLOYEE One-to-one relationship

24. Entity-Relationship Diagram EMPLOYEE DEPARTMENT is a member of contains Many EMPLOYEES are members of a DEPARTMENT One DEPARTMENT contains many EMPLOYEES Many-to-one relationship

25. Entity-Relationship Diagram

26. Entity-Relationship Diagram Relationships are normally given names that are verbs, while attributes and entities are named after nouns. This convention makes it easy to express relationships. For example, if we name our Person/City relationship "Lives In", we can string them together to say "A person lives in a city." We express relationships in E-R diagrams by drawing a line between the related entities and placing a diamond shape that contains the relationship name in the middle of the line. Here's how our Person/City relationship would look: 

27. Data Dictionary •A structured place to keep details of the contents of data flows, processes, and data store. •It is a structured repository of data about data. •It is a set of definitions of all DFD elements

28. Advantages of Data Dictionary •Documentation- it is a valuable reference in any organization. •It improves analyst/user communication by establishing consistent definitions of various elements, terms and procedures •It is important step in building a database