Data Flow Diagrams - Examples And Franchise Colleges Data Flow Diagrams - Examples Using SSADAM Notation By MANSHA NAWAZ DFD - Examples

Context Diagram Order Company Customer Rejected Order Despatch Note + Goods DFD - Examples

Maintain Credit Ratings 2 Warehouse A Complete DFD 1 Sales Order Check Credit Rating Customer Rejected Order D1 Credit Rating Dispatch Note Accounts 3 Maintain Credit Ratings 2 Warehouse Dispatch Goods DFD - Examples

Data Flow Diagrams (DFDs) show: The processes within the system The datastores (files) supporting its operation The information flows within it The system boundary Interactions with external entities DFD - Examples

A Data Flow Customer DFD Symbols SSADM Notation An External Entity Sales 3 A Process Check Credit Rating D1 Credit Rating A Data Store DFD - Examples

The Process Symbol Unique Number Where it’s done 3 Sales Input Data Check Credit Rating Output Data What’s done DFD - Examples

Maintain Credit Rating Reading The data store symbol D1 Credit Rating Writing/Updating Accounts 3 Maintain Credit Rating Reading 1 Sales M = Manual data Store D = Computer File Check Credit Rating DFD - Examples

Self Evident Data Flows need not be named The Data Flow Symbol Use Meaningful names Customer Balance Self Evident Data Flows need not be named D1 Credit Rating Sales 3 Check Credit Rating DFD - Examples

Physical Resource Flow Customer Returned Library Book DFD - Examples

The External Entity Symbol System Boundary The External Entity Symbol Customer A Source and/or sink of data outside the system boundry DFD - Examples

Levelling – to avoid complex DFDs, processes can be grouped into higher level processes 2 Dispatch Goods Process 2.1 Validated Order 1 Dispatch Note 2 DFD - Examples

Maintain Credit Ratings 2 Warehouse A Complete DFD 1 Sales Order Check Credit Rating Customer Rejected Order D1 Credit Rating Dispatch Note Accounts 3 Maintain Credit Ratings 2 Warehouse Dispatch Goods DFD - Examples

Repeated Symbols – to avoid crossing lines, data stores and external entities can be repeated: Customer Customer A Duplicated External Entity D1 Credit Rating Duplicated Data Store DFD - Examples

DFD Levels Elementary Functional Description Level 2 E F D Level 1 Get cust dets If order>cred refer Else raise order ….. E F D Level 1 DFD - Examples

Wines & Spirits Example A wines and spirits wholesaler stocks a range of approximately 400 different lines and delivers by van on regular weekly runs to customers who are mainly off-licenses and clubs. The majority of orders are received by telephone and any one customer may place several orders during the week which must be accumulated and delivered in one consignment. When a customer telephones he expects to be advised on the availability of an item requested and, if not in stock, the alternatives that are available. At present, sales order forms are filled in by the telephone salesmen and sent to the warehouse where they are used for the despatch of the items. Hand-written despatch notes are used as the basis of the invoices which are typed and sent by post sometime later. Prepare a dataflow diagram (DFD) which represents the above system. DFD - Examples

Developing Dataflow Diagrams 1. Identify external entities 2. Draw context diagram 3. Who/Where does what 4. Identify datastores 5. Draw diagram DFD - Examples

External Entities Customer Context Diagram order advice customer company des. note + goods invoice DFD - Examples

Accumulate orders Sales Advise availability Sales What Where/who Receive orders Sales Accumulate orders Sales Advise availability Sales Complete Sales Order Form Sales Despatch Items Warehouse Write despatch notes Warehouse Type Invoices Warehouse Send Invoices Warehouse Datastore Stock file DFD - Examples

Draw DFD DFD - Examples customer Stock file customer Order Advice 1 Sales Stock file M1 Accumulate orders Advise availability Complete forms Sales Order Forms Warehouse 2 Produce despatch notes Produce Invoices Despatch note + goods Invoice customer DFD - Examples

Maintenance of Stock File Customer file – address, credit etc Payments Extensions Maintenance of Stock File Customer file – address, credit etc Payments Accounts dept – invoices, payments etc Accumulate orders – temporary file DFD - Examples

Draw DFD DFD - Examples Customer 1 Sales Customers Stock file M1 M2 Order Advice 1 Sales Customers Stock file M1 M2 Accumulate orders Advise availability Complete forms Confirm details Sales Order Forms Payments Orders M3 Warehouse M4 2 Pick Goods Produce Despatch Notes Update Stock File Accounts 3 Copy Dispatch Note Produce Invoices Handle payments Goods + Copy Order Payment Despatch Note + Goods Supplier Invoice D/N + Inv M5 Customer DFD - Examples

Name Alias Type Length Max Min Data Dictionary Name Alias Type Length Max Min Custno Custnum Num 10 ItemDes ItemDesc Alp 20 OrdTot TotOrd Cur 5 999 9 e.t.c. DFD - Examples

Comes in various editions to match the methodology used (SSADM) SELECT (SSADM) A software package for the development of data flow diagrams and data models etc. Comes in various editions to match the methodology used (SSADM) Check compatibility between DFD and LDS Checks DFD level compatibility FREE to copy from library short term loan (need to sign license agreement and get key from CEMS Help Desk) DFD - Examples

SSADM Structured Systems Analysis And Design Methodology A highly structured IS development methodology with the emphasis on analysis and design including the user but little about writing programs, testing or implementation. DFD - Examples

Fastfood Example The example below is an illustration of the data flow in a takeaway restaurant.  The order is taken on a carbon pad, the cost is calculated from the menu, the order is checked with the customer, if OK the order is stuck on a pin-board.  When the food is ready, the order becomes the delivery note for the driver.  At the close of business, carbons are used to update accounts and then dumped along with the delivery notes.  Management information is passed to the manager. DFD - Examples

Fast Food Delivery System 1 Meal and Customer details Meal and Customer details Record Order D1 Carbon pad Look up meal Customer Price of meal 2 Record prices Calculate Order D2 Menu New price Look up prices Details 3 Re-check Order Prices D3 Pin 1 Carbon details Signature *second copy goes on Pin2 as a backup Manager 4 Deliver Order D4 Delivery Sheet Name, ticket no.and price Daily sales Retrieve carbon 5 Calculate All Orders Account Book D5 Meal total Fast Food Delivery System Current System Level 1 DFD Retrieve delivery sheet 6 Pin2 D6 Delete All Orders Dump carbon 7 D7 Waste Bin DFD - Examples Delete Delivery Sheet Dump delivery sheet

Process 1 – Record Order Details Current System – Level 2 Process 1 – Record Order Details Customer Record Meal Details 1.1 1 3 Carbon Pad D1 4 4 2 Record Customer Details 1.2 D2 Menu Fast Food Delivery System Current System Level 2 DFD Notes: Customer gives meal details (1) and prices are looked up (2) in the menu before being added (3) to the carbon pad. Customer details such as address etc. are then added (4) to the carbon pad. DFD - Examples

Process 1.1 – Record Meal Details Current System – Level 3 Process 1.1 – Record Meal Details 1.1.1 Customer Add New Meal to Order Carbon Pad D1 1 1 1 1.1.2 2 Amend Order Meal Details Menu D2 1 1.1.3 Delete Order 2 Waste Bin D6 Fast Food Delivery System Current System Level 3 DFD Notes: During a call the customer can simply add meals to her or his order which go straight onto the carbon pad. However, they could also change their mind (1) in which case new prices need to be looked up and the original carbon entry changed. They may even want to cancel the order (2). Level 2 UNCHANGED data flows are shown in blue DFD - Examples

Process 1.2 – Record Customer Details Current System – Level 3 Process 1.2 – Record Customer Details 1.2.1 Customer Customer Details Add New Customer Details Carbon Pad D1 Changes to Customer Details Amend Customer Details 1.2.2 Fast Food Delivery System Current System Level 3 DFD Notes: During a call the customer’s details – name, address etc. are added to the carbon pad. However, during the call it may be necessary to amend their details (for example, if the telephone operator has misheard the original details. Level 2 UNCHANGED data flows are shown in blue DFD - Examples

Process 2 – Calculate Order Value Current System – Level 2 Process 2 – Calculate Order Value 2.1 Customer Meal Details Record Meal Prices Carbon Pad D1 Prices All Prices Total cost Of meal 2.2 Menu D2 Calculate Order Value Fast Food Delivery System Current System Level 2 DFD Notes: During a call individual meal prices are looked up in the menu and added to the carbon pad. On completion of an order the prices of all ordered meals, on the pad, are added together to give the total cost of the meal. This is then relayed to the customer. DFD - Examples

Process 3 – Re-check Order Current System – Level 2 Process 3 – Re-check Order 3.1 Customer Meal Details Amend Meal Details Carbon Pad D1 Customer Details 3.2 New Price of Order Amend Customer Details Menu D2 3.3 Recalculate Order Fast Food Delivery System Current System Level 2 DFD Notes: After an order is complete the customer may ring up to check they have given the correct details or to amend an order (forgotten the prawn crackers!) In this case details on the carbon pad are checked and amended as necessary before the customer is given the new price of the order. DFD - Examples

Process 3.1 – Amend Meal Details Current System – Level 3 Process 3.1 – Amend Meal Details 3.1.1 Customer New Meal Details Add New Meal to Order Carbon Pad D1 Changes to Ordered Meals 3.1.2 Amend Order Meal Details Menu D2 Customer and Order Details 3.1.3 Delete Order Waste Bin D7 Fast Food Delivery System Current System Level 3 DFD Notes: After an order has been taken the customer may telephone to amend order details. She could ask to add new meals or amend meals and prices will have to be looked up in the menu. Or, she can cancel the order in which case it is consigned to the waste bin. DFD - Examples

Process 4 – Deliver Order Current System – Level 2 Process 4 – Deliver Order 4.1 Customer Complete Delivery Sheet Pin1 D3 Customer Signature 4.2 Delivery Sheet D4 Obtain Customer Signature Fast Food Delivery System Current System Level 2 DFD Notes: When the order is ready for delivery the carbon on Pin1 is used to complete the drivers delivery sheet – customer details, cost of order. On delivery of the order the customer is asked to sign the delivery sheet. DFD - Examples

Process 5 – Calculate All Orders Current System – Level 2 Process 5 – Calculate All Orders Pin1 D3 Order Values Calculate All Orders 5.1 Total Sales Manager Total sales Account Book D5 Fast Food Delivery System Current System Level 1 DFD Notes: At the close of business all orders that have been taken during the day (carbons) are taken from Pin 1 and the total value of daily business is calculated manually (using a calculator) by the Accounts person. This information is passed onto the restaurant manager. DFD - Examples

Process 6 – Delete All Orders Current System – Level 2 Process 6 – Delete All Orders 6.1 Delete Original Copies Pin 1 D3 6.2 Delete Duplicate Copies Pin 2 D6 Waste Bin D7 Fast Food Delivery System Current System Level 2 DFD Notes: At the close of business all original and duplicate copies of orders (carbons) are removed from the pins and disposed of. DFD - Examples