data flow diagrams ipt 2010. data flow diagrams a data flow diagram provides more detail at a lower...
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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