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

Worked Example Students send in an application form containing their personal details and their desired course. Details of all applications that are received are recorded in the applications file.Students send in an application form containing their personal details and their desired course. Details of all applications that are received are recorded in the applications file. The college checks that the course is available by looking up the course file. The college also checks that the student has necessary academic qualifications for the course.The college checks that the course is available by looking up the course file. The college also checks that the student has necessary academic qualifications for the course. If the course is available and student has the necessary entry requirements, the student is enrolled in the course and the college confirms the enrolment by sending a confirmation letter to the student. The student details are added to the Enrolment File.If the course is available and student has the necessary entry requirements, the student is enrolled in the course and the college confirms the enrolment by sending a confirmation letter to the student. The student details are added to the Enrolment File. If the course is unavailable or the student does not have the necessary academic qualifications the college sends the student a rejection letter. The relevant entry in the Application File is updated to show that the applicant has been unsuccessful.If the course is unavailable or the student does not have the necessary academic qualifications the college sends the student a rejection letter. The relevant entry in the Application File is updated to show that the applicant has been unsuccessful.

Your Turn – Order Processing When they place their first order, customer details are taken by the orders clerk and added to the Customer File, The orders clerk takes order details from customers over the phone, by or by fax. Details of every order are added to the Orders Folder and a copy of the order is made.When they place their first order, customer details are taken by the orders clerk and added to the Customer File, The orders clerk takes order details from customers over the phone, by or by fax. Details of every order are added to the Orders Folder and a copy of the order is made. The orders clerk uses the order copy to complete a picking slip. He sends this to the warehouse together with the copy of the order.The orders clerk uses the order copy to complete a picking slip. He sends this to the warehouse together with the copy of the order. At the warehouse, the goods are set up for dispatch in the loading bay. The picking slip is sent back to the orders clerk along with the copy order.At the warehouse, the goods are set up for dispatch in the loading bay. The picking slip is sent back to the orders clerk along with the copy order. 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 is sent to the warehouse so that the goods can be dispatched to the customer.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 is sent to the warehouse so that the goods can be dispatched to the customer.

How to create a Level 0 dfd. Make the following headings in your jotter:Make the following headings in your jotter: –System Name; –External Entities; –Data Flow; & –Physical Flow. Go through the passage and write down any of the above under the headings.Go through the passage and write down any of the above under the headings.

Worked Example - Enrolment System NameSystem Name –College Enrolment External EntitiesExternal Entities –Student Data Flow (between external entity and system)Data Flow (between external entity and system) –Application form –Acceptance Letter –Rejection Letter Physical FlowPhysical Flow Now you do Your turn -

Your Turn – Order Processing System NameSystem Name –Order Processing External EntitiesExternal Entities –Customer –Warehouse Data FlowData Flow –Order –Customer Details –Picking Slip/Copy of Order (2) –Invoice –Shipping Statement Physical FlowPhysical Flow

How to create a Level 0 dfd. The system name goes in a hard box in the middle of the page.The system name goes in a hard box in the middle of the page.

How to create a Level 0 dfd. Each external entity goes in an oval box either to: the left and right if there are two; left, right and bottom if there are three; or left right bottom and above if there are 4.Each external entity goes in an oval box either to: the left and right if there are two; left, right and bottom if there are three; or left right bottom and above if there are 4. Entity 1Entity 2 Entity 3

Worked Example – College Enrolment College Enrolment Student Now you do Your turn -

Your Turn – Order Processing Order Process CustomerWarehouse

How to create a Level 0 dfd. Add in data flow:Add in data flow: –use a thin line with an arrow showing the way the data flows. –write the name of the data flow on the line. Add in physical flow:Add in physical flow: –use a thick line with an arrow showing the way the physical flows. –write the name of the physical flow on the line.

Worked Example – College Enrolment College Enrolment Student Now you do Your turn - Application Acceptance Letter Rejection Letter

Your Turn – Order Processing Order Processing CustomerWarehouse Customer Details Order Picking Slip Copy of Order Picking Slip Copy of Order Warehouse Shipping Statement Invoice

Well Done! That is how you create level 0 DFD’s

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

How to create Level 1 dfd’s When creating a level 1 dfd go back and read the description! (VERY IMPORTANT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !)When creating a level 1 dfd go back and read the description! (VERY IMPORTANT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !) Write down the following Headings:Write down the following Headings: External EntityExternal Entity ProcessesProcesses Data FlowsData Flows Data StoresData Stores

How to create Level 1 dfd’s As you read through the passage (again) write down the relevant information under the headings above.As you read through the passage (again) write down the relevant information under the headings above. This will be used as a check list after creating the dfd.This will be used as a check list after creating the dfd.

Worked Example – School 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 – School 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 Now you do Your turn -

Your Turn – Order Processing 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

Your Turn – Order Processing 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)

How to create Level 1 dfd’s Processes are drawn using a Hard Box :Processes are drawn using a Hard Box : Files are drawn as follows:Files are drawn as follows: D1 Data Flow is drawn the same as at level 0.Data Flow is drawn the same as at level 0.

How to create Level 1 dfd’s Read each sentence of the description carefully.Read each sentence of the description carefully. As you read the sentence draw that part of the dfd using the key on the previous page.As you read the sentence draw that part of the dfd using the key on the previous page. When you have finished use your checklist to make sure you have included all your processes, files etc.When you have finished use your checklist to make sure you have included all your processes, files etc.

Working Example – Student enrolment student application Application Processing D1 Application FileAdd application details Check course Details D2 Course details Course Details Course Details File Check student Qualifications Student details Course Details Enrolment Process Confirmation letter Checking results D3 Enrolment File Student Details D1 Application File Update rejection letter Your turn – order processing

Your Turn – Order Processing Customer Order Processing D1 Customer File Add customer details Customer Details orders M1 Order Folder Order details Complete Picking Slip Warehouse Copy of Order Picking Slip Copy of order Picking Slip Create invoice/ Shipping statement Copy of order Invoice Shipping Statement

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

Your Turn – Schoo System 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.