Data Flow Diagrams (DFDs) Level 1
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Questions and Answers

What is the main difference between a context diagram and a Level 1 DFD?

  • The number of external entities depicted
  • The type of symbols used to represent processes
  • The number of data stores shown
  • The level of detail in illustrating internal mechanisms (correct)

    • What does the 'D' symbol represent in a Level 1 DFD?

  • External entity
  • Manual data store
  • Digital data store (correct)
  • Temporary data store

    • Why is it important to draw separate external entities for each role in a system?

  • To show data flows between external entities
  • To illustrate internal mechanisms
  • To reduce the number of external entities
  • To avoid confusion and ensure clarity (correct)

    • What is the purpose of drawing both positive and negative cases in a system?

    <p>To consider all possible scenarios and outcomes</p> Signup and view all the answers

    What is the symbol used to illustrate an external entity in a Level 1 DFD?

    <p>Ellipse</p> Signup and view all the answers

    What is the purpose of a Level 1 DFD in system design?

    <p>To detail internal mechanisms and data flows</p> Signup and view all the answers

    What is the primary purpose of identifying external entities in a system?

    <p>To initiate a process</p> Signup and view all the answers

    When drawing a Level 1 DFD, what assumption should be made about a person's role?

    <p>A person can have one or more roles</p> Signup and view all the answers

    What can be considered a data store?

    <p>Any type of data storage, including paper-based records</p> Signup and view all the answers

    What is the difference between a 'T' and an 'M' symbol in a Level 1 DFD?

    <p>T represents a temporary data store, while M represents a manual data store</p> Signup and view all the answers

    What is a characteristic of a process in a system?

    <p>It is an action done by an internal personnel or subsystem</p> Signup and view all the answers

    What is a rule for data flow in a system?

    <p>Data flow must be from an entity to a process or a process to an entity</p> Signup and view all the answers

    What is a requirement for every process in a system?

    <p>It must have at least one input data flow and one output data flow</p> Signup and view all the answers

    What is a requirement for every data store in a system?

    <p>It must have at least one input data flow and one output data flow</p> Signup and view all the answers

    What is a rule for linking processes in a system?

    <p>All processes must be linked to at least one data store or another process</p> Signup and view all the answers

    What is not allowed in a data flow diagram?

    <p>Two data flows crossing each other</p> Signup and view all the answers

    What is the primary purpose of creating a requirements specification document in SSADM?

    <p>To communicate between different stakeholders within the development process</p> Signup and view all the answers

    What type of diagram is used to show the flow of data between different system entities?

    <p>Data Flow Diagram (DFD)</p> Signup and view all the answers

    What is the highest level of modeling in Data Flow Diagrams (DFDs)?

    <p>Level 0 DFD (Context Diagrams)</p> Signup and view all the answers

    What is the purpose of a Context Diagram in Data Flow Diagrams (DFDs)?

    <p>To show data flows between the system and external entities only</p> Signup and view all the answers

    What is NOT a type of illustration or plan used in Logical Design?

    <p>Requirements Specification</p> Signup and view all the answers

    What is an entity in the context of software development?

    <p>Anything including human, place, vehicle, animal or another system</p> Signup and view all the answers

    How many types of Data Flow Diagrams (DFDs) can be listed?

    <p>2</p> Signup and view all the answers

    What is the purpose of Logical Design in the development of an information system?

    <p>To make plans and high-level illustrations of the system</p> Signup and view all the answers

    Study Notes

    Data Flow Diagrams (DFDs)

    • DFDs are used to show the flow of data between different system entities.
    • Entities in software development can be humans, places, vehicles, animals, or other systems.

    Level 1 DFD

    • Used to illustrate internal mechanisms as well as external entity data flows.
    • More in-detailed than context diagrams.
    • Uses different symbols from context diagrams.

    Symbols Used in Level 1 DFD

    • To illustrate a process
    • To illustrate a data store (types: digital, manual, temporary)
    • To illustrate an external entity
    • To show data flows between the considering system and external entities
    • To show data flows between external entities

    Steps to Create Level 1 DFD

    • Care about internal processes, data stores, data flows, and external entities.
    • Find external entities first, as an entity only initiates a process.
    • A process is an action done by an internal personnel or internal subsystem.
    • A data store can be any type of data store (e.g., table written on paper).

    Level 1 DFD Rules

    • Data cannot flow between two entities.
    • Data flow must be from entity to a process or a process to an entity.
    • Data cannot flow between two data stores.
    • Data flow must be from data store to a process or a process to a data store.
    • Data cannot flow directly from an entity to a data store.
    • A process must have at least one input data flow and one output data flow.
    • Every process must have input data flow to process the data and an output data flow for the processed data.
    • A data store must have at least one input data flow and one output data flow.
    • Every data store must have input data flow to store the data and an output data flow for the retrieved data.
    • Two data flows cannot cross each other.
    • All processes in the system must be linked to at least one data store or another process.

    Requirements Specification

    • A crucial document outlining functional and non-functional requirements of the proposed information system in SSADM.
    • Includes functional requirements, non-functional requirements, constraints, assumptions and dependencies, etc.
    • The documentation process is the standard communication medium between different stakeholders within the development process.

    Logical Design

    • Includes making plans and high-level illustrations (modeling) in software development.
    • Examples include data flow diagrams, document flow diagrams, activity diagrams, flow charts, class diagrams, etc.

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    Related Documents

    infosysPrt2.pdf

    Description

    Learn about Data Flow Diagrams (DFDs) and their application in software development. Understand Level 1 DFDs, their symbols, and how they illustrate data flows between entities.

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