Data flow diagramsIPT 2010

data flow diagrams

A data flow diagram provides more detail at a lower then a context diagram. Data flow diagrams represent the information system as a number of processes that together form the single process of a context diagram.

DFD’s focus on the flow of data between information processes in a system.

Data flow diagrams

They show where data is collected, organised, analysed, stored, processed, transmitted and displayed.

DFD’s provide a simple technique for visualising the movement of data and describing what participants do, rather than what the computers do.

4 symbols used in A DATA FLOW DIAGRAM

ProceProcessss

ExternaExternall

EntityEntity

Data Flow

External Entity

Data Store DataStore

Process

Process

Process: A circle is used to represent the processes or actions that transform inputs to outputs.

ProcessProcess

data flow

Data Flow: An arrow is used to represent the flow of data between the process, external entity and data store.

External entity

External Entity: A square or a rectangle represents any person or organisation that sends data to or

receives data from the system.

ExternalExternalEntityEntity

Data store

Data Store: An open rectangle represents the location where data is

stored. It could be a filing cabinet, hard disk or DVD.

Data Store

examplefinding a book in a library

BorrowerBorrower SearcSearchh

BorrowerBorrower

LibraryDatabase

Book Details Call Number

Book Details

Call Number

ExampledOCTOR’S SYSTEM FOR INVOICING PATIENTS AFTER A

VISIT

Doctor’s record of Doctor’s record of visitvisit PatientsPatients MedicareMedicare

PatientPatientFee ScheduleFee Schedule

Patient’s Patient’s RecordsRecords

Medicare Medicare RecordsRecords

Accounts Accounts ReceivableReceivable

CalculaCalculatete

FeeFee

PreparPreparee

InvoicInvoicee

ReceivReceive e

PaymePaymentsnts

ACTIVITY

The marking system from the context diagram exercise is

extended to include a spreadsheet to store and moderate the marks.

Construct a data flow diagram to show the marking system.

textbook

Read pg. 270 and pg.271 and answer ‘Group Task- Discussion’

Answer Question 14 on pg.273