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IS 460 Notes. Documenting a System Analysis with Dataflow Diagrams By Thomas Hilton. System Analysis. The foundation skill of IS Professionals Understanding Whole Systems via the Systems View Outputs Information Other Inputs Data Other Processes Hardware Software People Procedures

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IS 460 Notes

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Is 460 notes

IS 460 Notes

Documenting a System Analysis with Dataflow Diagrams

By

Thomas Hilton


System analysis

System Analysis

  • The foundation skill of IS Professionals

  • Understanding Whole Systems via the Systems View

  • Outputs

    • Information

    • Other

  • Inputs

    • Data

    • Other

  • Processes

    • Hardware

    • Software

    • People

    • Procedures

  • User Perspective!


Systems are complex

Systems are Complex

  • They Can Only be Understood by “Functional Decomposition”

  • Invoke the System-Supersystem-Subsystem view

  • Alternate between the Black Box Concept and the Closed System Concept

  • Create Successive Levels of Detail


Information systems components

Information Systems Components

  • Entities External to the System

  • “Data” that Flows Through the System

  • Processes that Receive and Produce Data

  • “Data Stores” that store data


Information systems components1

Process name

x.x

Dx

Data Store Name

Information Systems Components

Entity Name

  • External Entity . . . . . . . . . .

  • Dataflow . . . . . . . . . . . . . .

  • Process . . . . . . . . . . . . . . .

  • Datastore . . . . . . . . . . . . .

Data Flow Name


Levels of detail

Levels of Detail

  • Context Level

  • Level 0

  • Levels 1, 2, etc.

  • Functional Primitive Level


Processes explode

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

x.x

Processes Explode

  • Each process at a higher level corresponds to a set of processes at the next lower level

Entity Name

Entity Name


Some traits of the example

Some Traits of the Example

  • Every dataflow starts somewhere and ends somewhere

  • Dataflows at a lower level agree with the dataflows of their parent process

  • No dataflow exits and enters the same process

  • Every process has at least one input and at least one output

  • Every process explodes to at least two subprocesses

  • Some processes don’t explode; these are called functional primitives, and they contain pseudocode


Pseudocode the right idea

Pseudocode, the Right Idea…

  • Pseudo = fake, false

  • Code = software instructions

    Select NAME, ADDRESS

    From TABLE

    Where CREDIT_LIMIT .GE. 10000

Fake variable names

Fake table name

Incorrect syntax

Fake conditions


Questions

Questions?

On to an Example!


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