Data Flow Diagrams Topic 3 – Data Modelling Techniques Unit 1 – Database Analysis and Design Advanced Higher Information Systems St Kentigern’s Academy

Data Flow DiagramsData Flow Diagrams

Topic 3 – Data Modelling Topic 3 – Data Modelling TechniquesTechniques

Unit 1 – Database Analysis and Unit 1 – Database Analysis and DesignDesign

Advanced Higher Information Advanced Higher Information SystemsSystems

St Kentigern’s AcademySt Kentigern’s Academy

Worked ExampleWorked Example• Students send in an application form containing their personal Students send in an application form containing their personal

details and their desired course. Details of all applications that details and their desired course. Details of all applications that are received are recorded in the applications file.are received are recorded in the applications file.

• The college checks that the course is available by looking up the The college checks that the course is available by looking up the course file. The college also checks that the student has course file. The college also checks that the student has necessary academic qualifications for the course.necessary academic qualifications for the course.

• If the course is available and student has the necessary entry If the course is available and student has the necessary entry requirements, the student is enrolled in the course and the requirements, the student is enrolled in the course and the college confirms the enrolment by sending a confirmation letter college confirms the enrolment by sending a confirmation letter to the student. The student details are added to the Enrolment to the student. The student details are added to the Enrolment File.File.

• If the course is unavailable or the student does not have the If the course is unavailable or the student does not have the necessary academic qualifications the college sends the student necessary academic qualifications the college sends the student a rejection letter. The relevant entry in the Application File is a rejection letter. The relevant entry in the Application File is updated to show that the applicant has been unsuccessful.updated to show that the applicant has been unsuccessful.

Your Turn – Order Your Turn – Order ProcessingProcessing

• When they place their first order, customer details are taken by When they place their first order, customer details are taken by the orders clerk and added to the Customer File, The orders the orders clerk and added to the Customer File, The orders clerk takes order details from customers over the phone, by clerk takes order details from customers over the phone, by email or by fax. Details of every order are added to the Orders email or by fax. Details of every order are added to the Orders Folder and a copy of the order is made.Folder and a copy of the order is made.

• The orders clerk uses the order copy to complete a picking slip. The orders clerk uses the order copy to complete a picking slip. He sends this to the warehouse together with the copy of the He sends this to the warehouse together with the copy of the order.order.

• At the warehouse, the goods are set up for dispatch in the At the warehouse, the goods are set up for dispatch in the loading bay. The picking slip is sent back to the orders clerk loading bay. The picking slip is sent back to the orders clerk along with the copy order.along with the copy order.

• The order clerk uses the order copy to make up an invoice and The order clerk uses the order copy to make up an invoice and shipping statement. The invoice is sent to the customer and shipping statement. The invoice is sent to the customer and shipping statement is sent to the warehouse so that the goods shipping statement is sent to the warehouse so that the goods can be dispatched to the customer.can be dispatched to the customer.

How to create a Level 0 How to create a Level 0 dfd.dfd.

• Make the following headings in your Make the following headings in your jotter:jotter:– System Name;System Name;– External Entities;External Entities;– Data Flow; &Data Flow; &– Physical Flow.Physical Flow.

• Go through the passage and write Go through the passage and write down any of the above under the down any of the above under the headings.headings.

Worked Example - Worked Example - EnrolmentEnrolment

• System NameSystem Name– College EnrolmentCollege Enrolment

• External EntitiesExternal Entities– StudentStudent

• Data Flow (between external entity and Data Flow (between external entity and system)system)– Application formApplication form– Acceptance LetterAcceptance Letter– Rejection LetterRejection Letter

• Physical FlowPhysical Flow Now you do Your turn -


• System NameSystem Name– Order ProcessingOrder Processing

• External EntitiesExternal Entities– CustomerCustomer– WarehouseWarehouse

• Data FlowData Flow– OrderOrder– Customer DetailsCustomer Details– Picking Slip/Copy of Order (2)Picking Slip/Copy of Order (2)– InvoiceInvoice– Shipping StatementShipping Statement

• Physical FlowPhysical Flow


• The system name goes in a hard box The system name goes in a hard box in the middle of the page.in the middle of the page.

<system name>


• Each external entity goes in an oval box either to: Each external entity goes in an oval box either to: the left and right if there are two; left, right and the left and right if there are two; left, right and bottom if there are three; or left right bottom and bottom if there are three; or left right bottom and above if there are 4.above if there are 4.

<System Name>Entity 1 Entity 2

Entity 3

Worked Example – Worked Example – College EnrolmentCollege Enrolment

College EnrolmentStudent

Now you do Your turn -


Order ProcessCustomer Warehouse


• Add in data flow: Add in data flow: – use a thin line with an arrow showing the use a thin line with an arrow showing the

way the data flows.way the data flows.– write the name of the data flow on the write the name of the data flow on the

line. line.

• Add in physical flow:Add in physical flow:– use a thick line with an arrow showing use a thick line with an arrow showing

the way the physical flows.the way the physical flows.– write the name of the physical flow on write the name of the physical flow on

the line.the line.

Worked Example – Worked Example – College EnrolmentCollege Enrolment

College EnrolmentStudent


Application

AcceptanceLetter

RejectionLetter


Order ProcessingCustomer Warehouse

Customer Details

Order

Picking Slip

Copy of Order

Picking Slip

Copy of Order

Warehouse

Shipping Statement

Invoice

Well Done!Well Done!

That is how you create That is how you create level 0 DFD’slevel 0 DFD’s

What is a Level 1 dfd’sWhat is a Level 1 dfd’s

• A level 1 dfd is a diagramatic A level 1 dfd is a diagramatic form of showing the main form of showing the main processes, data flows and data processes, data flows and data stores within the system.stores within the system.

How to create Level 1 How to create Level 1 dfd’sdfd’s

• When creating a level 1 dfd go back When creating a level 1 dfd go back and read the description! (VERY and read the description! (VERY IMPORTANT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !)IMPORTANT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !)

• Write down the following Headings:Write down the following Headings:• External EntityExternal Entity• ProcessesProcesses• Data FlowsData Flows• Data StoresData Stores


• As you read through the passage As you read through the passage (again) write down the relevant (again) write down the relevant information under the headings above.information under the headings above.

• This will be used as a check list after This will be used as a check list after creating the dfd.creating the dfd.

Worked Example – Worked Example – School EnrolmentSchool Enrolment

• External EntityExternal Entity• StudentStudent

• ProcessesProcesses• Record student applicationRecord student application• Check course availabilityCheck course availability• Check student qualificationsCheck student qualifications• Enrol student in courseEnrol student in course• Update application fileUpdate application file

Worked Example – Worked Example – School EnrolmentSchool Enrolment

• Data FlowsData Flows• Application formApplication form• Course Applied forCourse Applied for• Student QualificationsStudent Qualifications• Results from course and student checksResults from course and student checks• Course and student detailsCourse and student details• Confirmation letterConfirmation letter• Rejection letterRejection letter

• Data StoresData Stores• Application fileApplication file• Course Details FileCourse Details File• Enrolment FileEnrolment File



• External EntityExternal Entity• CustomerCustomer• WarehouseWarehouse

• ProcessesProcesses• Process order detailsProcess order details• Complete picking slipComplete picking slip• Process invoice and shipping statementProcess invoice and shipping statement


• Data FlowsData Flows• Customer details (2)Customer details (2)• Order details (2)Order details (2)• Picking slip (2)Picking slip (2)• Order Copy (3)Order Copy (3)• InvoiceInvoice• Shipping statementShipping statement

• Data StoresData Stores• Customer File (D)Customer File (D)• Orders Folder (M)Orders Folder (M)


• Processes are drawn using a Hard Processes are drawn using a Hard Box :Box :

• Files are drawn as follows:Files are drawn as follows:

<process1>

D1 <File 1>

• Data Flow is drawn the same as Data Flow is drawn the same as at level 0.at level 0.


• Read each sentence of the description Read each sentence of the description carefully.carefully.

• As you read the sentence draw that As you read the sentence draw that part of the dfd using the key on the part of the dfd using the key on the previous page.previous page.

• When you have finished use your When you have finished use your checklist to make sure you have checklist to make sure you have included all your processes, files etc.included all your processes, files etc.

Working Example – Working Example – Student enrolmentStudent enrolment

student

applicationApplication Processing

D1 Application FileAdd application details

Check courseDetails

D2

Course details

Course Details

Course Details File

Check studentQualifications

Student details

Course Details

Enrolment Process

Confirmationletter

Checking results

D3 Enrolment FileStudent Details

D1 Application File

Update

rejectionletter

Your turn – order processing


Customer

Order Processing

D1 Customer File

Add customerdetails

CustomerDetails

orders

M1 Order FolderOrder details

Complete Picking Slip

Warehouse

Copy of Order

Picking SlipCopy of order

Picking Slip

Create invoice/Shipping statement

Copy oforderInvoice

Shipping Statement

• Way Hey – Now you can do level 1 Way Hey – Now you can do level 1 dfd’s! Well Done!dfd’s! Well Done!

Your Turn – Schoo Your Turn – Schoo SystemSystem

• The Head Teacher’s secretary runs the system alone. When parents submit an application for a pupil to join the school, the pupil’s details are added to the applications file. The secretary sends out a letter to the pupil’s music teacher asking for a reference.

• When the secretary has received the reference, a decision is made whether to offer a place to the pupil. A letter is sent to the parents either offering a place or declining the application, and the applications file is updated to show the result of the application. If a place has been offered, the secretary will have checked the classes file, and included details of a start date in the offer letter. The pupil’s details will have been added to the admissions file, the admission shown as “offered” and the classes file updated to show one less place.

• If the parents accept the place, the pupil is admitted: the admission is changed to “accepted” and their details are added to the pupil file. If they do not accept the place, the admission is changed to “declined” and the classes file is updated to free up a place.

Documents

Data Flow Diagrams Topic 3 – Data Modelling Techniques Unit 1 – Database Analysis and Design Advanced Higher Information Systems St Kentigern’s Academy