Data Flow Diagrams - What is DFD? Data Flow Diagram Symbols and More

00:04:14
https://www.youtube.com/watch?v=6VGTvgaJllM

摘要

TLDRThis video provides an introduction to data flow diagrams (DFDs), which illustrate how data is processed in a system by showing inputs, outputs, and storage. Originating in the 1970s, DFDs are mainly classified into two types based on notation: Jordan and De Marco’s, which depicts processes as circles, and Gane and Sarson’s, which uses rounded squares. The video explains common symbols such as process notations, data stores, data flows, and external entities. DFDs are structured in levels, starting with a context diagram that outlines the system's overall function then detailing the data flow through successive levels. Automated tools like SmartDraw can facilitate the construction of DFDs, providing templates and symbols for easy building.

心得

  • 🔄 DFDs illustrate data processing within a system.
  • 🔍 Two main notations: Jordan and De Marco, Gane and Sarson.
  • ⚙️ Common symbols include process, data store, data flow, and external entity.
  • 📊 Context diagrams give a top-level overview of system functions.
  • 🛠️ Tools like SmartDraw make DFD construction easy with templates.

时间轴

  • 00:00:00 - 00:04:14

    This section introduces data flow diagrams (DFDs), explaining their purpose in visualizing how data is processed within a system. It highlights that DFDs focus on the flow of information, detailing its origins, destinations, and storage. DFDs rose to prominence in the 1970s, thanks to Larry Constantine and Edie Jordan's work on structured design, which predated UML diagrams.

思维导图

视频问答

  • What is a data flow diagram?

    A data flow diagram illustrates how data is processed by a system in terms of inputs and outputs.

  • What are the main types of notations for DFDs?

    The main types are Jordan and De Marco’s notation and Gane and Sarson’s notation.

  • What symbols are commonly used in DFDs?

    Common symbols include process, data store, data flow, and external entity notations.

  • What is a context diagram?

    A context diagram is a top-level data flow diagram that contains only one process node representing the entire system.

  • How can you create a data flow diagram?

    You can create a data flow diagram using automated diagramming tools like SmartDraw.

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  • 00:00:04
    today we're talking about data flow
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    diagrams we'll examine what they're used
  • 00:00:10
    for what the various symbols and
  • 00:00:13
    notations mean and take a look at how to
  • 00:00:16
    get started building them a data flow
  • 00:00:18
    diagram illustrates how data is
  • 00:00:21
    processed by a system in terms of inputs
  • 00:00:23
    and outputs as its name indicates its
  • 00:00:27
    focus is on the flow of information
  • 00:00:29
    where data comes from where it goes and
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    how it gets stored data flow diagrams
  • 00:00:36
    became popular in the 1970s in software
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    development
  • 00:00:40
    they were first described in a classic
  • 00:00:43
    text about structured design written by
  • 00:00:45
    Larry Constantine and Edie Jordan what
  • 00:00:49
    became known as Jordan encodes
  • 00:00:52
    object-oriented analysis and design was
  • 00:00:55
    a way of visualizing software systems
  • 00:00:57
    before UML diagrams came along there are
  • 00:01:01
    essentially two different types of
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    notations for data flow diagrams Jordan
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    encode or gain in sarsen defining
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    different visual representations for
  • 00:01:11
    processes data stores data flow and
  • 00:01:14
    external entities Jordan encode type
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    data flow diagrams are usually used for
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    system analysis and design while gain
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    and SARS and type diagrams are more
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    common for visualizing information
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    systems visually the biggest difference
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    between the two is how processes look in
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    the yordan encode way processes are
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    depicted as circles while in the gain
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    and SARS and diagram the processes are
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    squares with rounded corners let's
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    explore the common data flow symbols and
  • 00:01:48
    notations and what they signify this is
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    a process notation a process transforms
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    incoming data flow into outgoing data
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    flow here is a data store notation data
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    stores are repositories of data in the
  • 00:02:04
    system they are sometimes also referred
  • 00:02:07
    to as just files this is a data flow
  • 00:02:11
    notation data flows are
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    lines through which packets of
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    information flow label the arrows with
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    the name of the data that moves through
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    it seen here is an external entity
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    notation external entities are objects
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    outside the system with which the system
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    communicates external entities are
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    sources and destinations of the system's
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    inputs and outputs data flow diagrams
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    also have levels or layers to help you
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    organize and categorize the data a
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    context diagram is a top level also
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    known as level 0 data flow diagram it
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    only contains one process node process 0
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    that generalizes the function of the
  • 00:02:56
    entire system in relationship to
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    external entities the next layer level 1
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    should illustrate a more detailed
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    analysis of the data in your context
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    diagram from there you'll go into still
  • 00:03:09
    more detail in level 2 and so on for the
  • 00:03:13
    next level break down your processes
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    until you reach pseudocode which is an
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    informal sort of coding language it has
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    the structure of programming language
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    but is meant for human reading not
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    machine reading dataflow diagrams are
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    pretty easy to construct using an
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    automated diagramming tool like smart
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    draw this will provide all the necessary
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    data flow diagrams symbols and easy to
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    use templates that help you get started
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    just drag and drop shapes where they
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    need to go and type to enter data you
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    can nest the different levels of your
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    data flow by using hyperlinks view our
  • 00:03:55
    how-to video to see a more detailed
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    example of a data flow diagram being
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    built from start to finish we hope
  • 00:04:03
    you've enjoyed learning about data flow
  • 00:04:05
    diagrams thanks for watching
  • 00:04:08
    [Music]
标签
  • data flow diagram
  • symbols
  • annotations
  • Jordan
  • Gane and Sarson
  • context diagram
  • data processing
  • inputs and outputs
  • visualization
  • automated tools