DATA FLOW DIAGRAMS (DFD): Sources and Sinks:

Presentation on theme: "DATA FLOW DIAGRAMS (DFD): Sources and Sinks:"— Presentation transcript:

1 DATA FLOW DIAGRAMS (DFD): Sources and Sinks:
Define System Boundaries Process (transformation) transforms data - no detail of how the transformation is done Inputs and Outputs Manual / Automated Process #, Brief descriptive label (action verb and object clause) (External Entities) Label 1. Receive Orders 1 Order Clerk: Order Entry # Desc. Who 1

2 Identifiers (letters,etc)
Data Store: only processes can connect to data stores A store is passive, process initiates flows Data Flow: # Invoices Invoices Identifiers (letters,etc) Name 2

3 DFD Example Orders Customers Invoices Customer Warehouse 1.
Invalid Orders Orders Orders Order Detail Goods info 1. Receive Order Shipping Detail Cust.Name, Address 2. Ship goods Cust.Name, Address Customers Billing Info Cust.Name, Address Invoices Goods info Invoice Statement Invoice Details 3. Collect Pmts Customer Pmt. Inquiries 3

4 (Implementation Model)
Data Store: may be a fundamental user requirement or an implementation store placed there for convenience. Order Detail Validated Order Process Order (Essential Model) Enter Order Acknowledgement xx yy Order Detail Process Order Enter Order Orders (Implementation Model) Acknowledgement 4

5 ? What transformation Update/Create Use/Retrieval Naming data Flows:
Orders Enter order ? What transformation Orders For Essential model name should be implementation free e.g. Course Request Form vs. Form23 5

6 Common DFD Errors Employee Member Accts. Employee file Accounts
Bank statement Membership application Create new member account 1. 3. Generate employee bank stat. Existing account Employee status Employee ID and address Member Accts. Employee file 2. Modified account status Freeze account number Accounts Receivable Dept Frozen acct. notification Common DFD Errors 6

7 Common DFD Errors: Process1 has inputs but produces no outputs. This is called a black hole Process 2 produces outputs but receives no inputs. This is called a miracle Process 3 has inputs and outputs ; however the inputs are not sufficient to produce the outputs. This is called a gray hole. 7

8 DFD Errors DF-2 E-1 DF-5 DF-1 DF-3 DF-6 DF-4 DF-2 E-2 1.0 P-1 DS1
DS Name DF-1 DF-3 DF-6 DF-4 2.0 P-2 DF-2 E-2 8

9 The Data Flow Packet Concept
Phone Company Itemized Calls Statement and Invoice Correct Use of Packet Concept Itemized Calls Statement Pay Phone Bill Invoice 9

10 Approved Credit Voucher
Diverging Data Flows Diverging data flows are implementation oriented and should be avoided on essential DFDs Customer Authorize Payment by Bank Card Credit Receipt Credit Vouchers Due Payments Customer Receipt Customer Authorize Payment by Bank Card Approved Credit Voucher Credit Vouchers Due Sale Payments 10

11 The Explosion Approach to drawing DFDs: As suggested by DeMarco and others, this diagramming technique requires the analyst to draw multiple DFDs, each one exploding from a single process on another diagram, until the system is completely modeled Context DFD A m Z The System p B n A C Z 1. 2. Overview DFD ZZZ E D B 3. A K 1.1. D B G 3.1 3.2 1.2 L 1.3 H XXX C M 1

12 Functional Decomposition and Leveled DFDs
Parent id 2.0 3.0 1.0 Explodes to Explodes to Child Child Level 1 Diagram 1 Level 1 Diagram 2 1.1 1.2 2.1 2.2 1.3 2.3 1.4 Explodes to Level 2 Diagram 1.4 1.4.1 1.4.2 1.4.3 1.4.4 Grandchild 2

13 TOP - DOWN analysis & functional decomposition
The System 1. function A 2. function B 1.1 Activity 1 of function A 1.2 Activity 2 of function A 2.1 Activity 1 of function B 2.2 Activity 2 of function B Task 1.1.1 Task 1.2.1 Task 2.2.1 Task 2.1.1 Task 1.2.2 Task 2.2.2 Task 1.1.2 Task 2.1.2 Task 2.2.3 Task 1.1.3 Decomposition Diagram 3

14 Top- Down Analysis and Functional Decomposition
Levelled Set of DFDs How many levels - not > 9 processes in single DFD Different parts of system can have different level of detail Consistency (Balancing) - inflow and outflow to process must correspond in next level DFD External entities,data stores,parent processes can, but need not be repeated in child diagram Data Stores at different levels - show data store at the highest level where it first serves as an interface between two or more processes Top- Down Analysis and Functional Decomposition 4

15 Carson-Plymouth Medical Devices (CPMD), as assembler of sophisticated medical products, must maintain a ready supply of high-quality components to manufacture its products. To achieve this goal, CPMD’s purchasing department checks inventory levels each day by reviewing the inventory items stock list. When the quantity-on-hand of a particular item reaches its economic reorder point, CPMD’s purchasing department places a purchase order with its supplier (supplier data is accessed through the supplier file) for that component and files a copy in the purchase order file. When a supplier delivers a shipment along with a bill of lading, shipping and receiving (S/R) receives the shipment by performing a three-step process. First, the S/R clerk verifies the shipment by accessing a copy of the purchase order and comparing it to the bill of lading. If a received item appears on the purchase order and the bill of lading, the verified bill of lading and received items are passed on to Inspection. Otherwise, the S/R clerk generates a notice of shipment error, which is sent to the supplier. Next, the inspector inspects the valid shipment items by accessing the quality criteria, from the inspection criteria folder. If the item meets all the quality criteria, the inspector adds it to an accepted items list, which is forwarded to the inventory clerk. If an item does not pass inspection, the inspector creates a notice of defective shipment, which is sent to the supplier along with the defective items. Finally, the inventory clerk updates the inventory items list by adding the current-on-hand quantity, reflecting an updated quantity. 5

16 Carson-Plymouth Medical Devices (CPMD), as assembler of sophisticated medical products, must maintain a ready supply of high-quality components to manufacture its products. To achieve this goal, CPMD’s purchasing department checks inventory levels each day by reviewing the INVENTORY ITEMS STOCK list. When the quantity-on-hand of a particular item reaches its economic reorder point, CPMD’s purchasing department places a purchase order with its supplier (supplier data is accessed through the SUPPLIER file) for that component and files a copy in the PURCHASE ORDER file. When a supplier delivers a shipment along with a bill of lading, shipping and receiving (S/R) receives the shipment by performing a three-step process. First, the S/R clerk verifies the shipment by accessing a copy of the purchase order and comparing it to the bill of lading. If a received item appears on the purchase order and the bill of lading, the verified bill of lading and received items are passed on to Inspection. Otherwise, the S/R clerk generates a notice of shipment error, which is sent to the supplier. Next, the inspector inspects the valid shipment items by accessing the quality criteria, from the INSPECTION CRITERIA folder. If the item meets all the quality criteria, the inspector adds it to an accepted items list, which is forwarded to the inventory clerk. If an item does not pass inspection, the inspector creates a notice of defective shipment, which is sent to the supplier along with the defective items. Finally, the inventory clerk updates the INVENTORY ITEMS list by adding the current-on-hand quantity, reflecting an updated quantity. 6

17 Process Ext. Entity Input Output Data Store
Carson-Plymouth Medical Devices (CPMD), as assembler of sophisticated medical products, must maintain a ready supply of high-quality components to manufacture its products. To achieve this goal, CPMD’s purchasing department checks inventory levels each day by reviewing the INVENTORY ITEMS stock list. Process Ext. Entity Input Output Data Store check inventory inventory levels from items to reorder inventory levels Inventory list items When the quantity-on-hand of a particular item reaches its economic reorder point, CPMD’s purchasing department places a purchase order with its supplier (supplier data is accessed through the SUPPLIER file) for that component and files a copy in the PURCHASE ORDER file. create a PO supplier items to reorder, PO to supplier, inv items supplier data PO to file supplier, from Supplier file PO 7

18 When a supplier delivers a shipment along with a bill of lading, shipping and receiving (S/R) receives the shipment by performing a three-step process. First, the S/R clerk verifies the shipment by accessing a copy of the purchase order and comparing it to the bill of lading. If a received item appears on the purchase order and the bill of lading, the verified bill of lading and received items are passed on to Inspection. Otherwise, the S/R clerk generates a notice of shipment error, which is sent to the supplier. Process Ext. Entity Input Output Data Store verify Supplier bill of lading; verified bill PO copy of PO of lading, notice of shipment errors to Supplier 8

19 Process Ext. Entity Input Output Data Store
Next, the inspector inspects the valid shipment items by accessing the quality criteria, from the INSPECTION CRITERIA folder. If the item meets all the quality criteria, the inspector adds it to an accepted items list, which is forwarded to the inventory clerk. If an item does not pass inspection, the inspector creates a notice of defective shipment, which is sent to the supplier along with the defective items. Process Ext. Entity Input Output Data Store Inspect Supplier verified bill of lading; accepted items Inspection Shipment inspection criteria list; defective Criteria from Inspection shipment notice Criteria Folder to Supplier 9

20 Process Ext. Entity Input Output Data Store
Finally, the inventory clerk updates the INVENTORY ITEMS list by adding the current-on-hand quantity, reflecting an updated quantity Process Ext. Entity Input Output Data Store Update Accepted items updated inv levels Inv. Items Inventory list, current inv. levels 10

21 Level 0 DFD Notice of defective shipment Notice of shipment error
Verify shipment 3. Supplier Bill of lading Create PO 2. P.O. Verified bill of lading PO info New PO data DS2 PO File Items to reorder Inspect shipment 4. Supplier data DS1 Supplier Inspection Criteria Check inv levels 1. DS2 Inspection Criteria Accepted items list Low items Updated data Update Inv. 5. DS4 Inventory Item Level 0 DFD Current Data

22 Level-1 DFD for Inspect Shipment Inspection criteria DS1 Supplier 4.1
Identify Inspection Criteria Item numbers, criteria 4.2 Inspect Items 4.3 Prepare notice of defective shipment Defective items data Notice of defective shipment Level-1 DFD for Inspect Shipment Accepted items list

23 Context and level 0 DFD When parts are received from vendors, they are accompanied by an invoice. Mrs Gauron in the Receiving Dept checks the invoice against the orders file to be certain that the correct parts were delivered. If the parts were not ordered or the order was incorrectly filled, parts are returned. If the parts are correct, the inventory file is updated to reflect the new quantity of these parts. This is done by increasing the data element quantity-on-hand by the quantity-record for the part-id . Mrs Gauron then prepares the payment for the vendor. She also enters the payment transaction in the general ledger, which is maintained as the bound accounting ledger. A worker on the factory floor who needs a part requests it by submitting a requisition to the parts clerk. The information on this form is used to update the inventory file. Each week the parts clerk uses the inventory file to prepare a report listing all parts whose quantity- on- hand has fallen below the reorder point. For parts listed on the report, a purchase request form is prepared and sent to the purchasing office. [ Hint: do not confuse the processes being performed with the people who perform them ] 14

24 Purchasing Office Vendor Floor
Context level DFD Purchasing Office Invoice Purchase Request Form 0. Inventory System Vendor Projected Part Requisition Floor Payment 15

25 General Ledger Order File 1. Vendor Check invoice Inventory 2. Update
Order record Order File Vendor 1. Check invoice Approved Invoice Rejected Part Part-id, Qty Inventory Payment 2. Update Part Qty Approved Invoice 3. Pay Vendor Used Part info Inv. record Payment Info 4. Provide part 5. Check part for reorder General Ledger 6. Prepare purchase request Requisition Purchasing office Reorder Info Floor Purchase request form 16

26 Level 1 DFD for functions related to the sales-order processing clerk
Delta Products Corporation is a major vendor of office supplies, furniture and equipment. Delta’s sales representatives call on customers to take orders. The sales rep write up the orders and turn them in to a sales order processing (SOP) clerk at the regional center. If the order items are in stock, the SOP clerk prepares a picking slip and packing list for each order. If any of the ordered items are out of stock, the SOP clerk completes an out of stock Notice forms, which notes the number of customer requiring the items and forwards it to Purchasing. A Purchasing clerk then completes a purchase order,which is mailed to a supplier. The SOP clerk notes back-ordered items on the customer’s order and forwards a copy of annotated customer order to Accounts receivable, where a A/R clerk prepares an invoice and sends it to the customer. The SOP clerk also forwards a picking slip and packing list to the warehouse, where stock price pickers fill the order,placing ordered items into boxes alongwith the packing list. The boxed items and packing list are held for delivery, usually via UPS. Context Diagram Level 0 DFD Level 1 DFD for functions related to the sales-order processing clerk 17

27 Level 0 DFD for Delta Products’ Order Fulfillment System
Invoice Customer EE-1 Order Information Write Order 1 Bill Customer 4 Supplier EE-2 Written Order Purchase Order Fill Order 3 Process Order 2.* Purchase Inventory 5 Annotated Order Packing List & Picking Slip Out of Stock Notice Updated Inventory Current Inventory UPS EE-3 D-1 Inventory Items Level 0 DFD for Delta Products’ Order Fulfillment System 18

28 Packing List & Picking Slip
Updated Inventory D-1 Inventory Items Current Inventory Written Order Check Item Availability 2.1 Prepare OoS Notice 2.3 Purchase Inventory 5 Out of Stock items order Out of Stock Notice Annotate Order (backordered items) 2.2 Bill Customer 4 In-Stock items order Annotated Order Prepare packing list & picking slip 2.4 Fill Order 3 Packing List & Picking Slip Level 1 Process Process Order 19