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Dfd examples
- 2. • A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system. • DFDs can also be used for the visualization of data processing (structured design). • It views a system as a function that transform the input into desired output .
- 3. • Flow chart shows “ flow of Control “ . • DFD shows “ flow of Data • The flowchart describes boxes that describe computations, decisions, interactions & loops. • It is important to keep in mind that data flow diagrams are not flowcharts and should not include control elements .
- 4. • Processes on DFDs can operate in parallel (at-the- same-time) o Processes on flowcharts execute one at a time • DFDs show the flow of data through a system o Flowcharts show the flow of control (sequence and transfer of control) • Processes on a DFD can have dramatically different timing (daily, weekly, on demand) o Processes on flowcharts are part of a single program with consistent timing
- 5. Creating Data Flow Diagrams Steps: 1. Create a list of activities 2. Construct Context Level DFD (identifies external entities and processes) 3. Construct Level 0 DFD (identifies manageable sub process ) 4. Construct Level 1- n DFD (identifies actual data flows and data stores ) 5. Check against rules of DFD
- 7. Creating Data Flow Diagrams Lemonade Stand Example
- 8. Creating Data Flow Diagrams Example Steps: The operations of a simple 1. Create a list of activities lemonade stand will be used 2. Construct Context Level DFD to demonstrate the creation (identifies sources and sink) of dataflow diagrams. 3. Construct Level 0 DFD (identifies manageable sub processes ) 4. Construct Level 1- n DFD (identifies actual data flows and data stores )
- 9. Creating Data Flow Diagrams Example 1. Create a list of activities Think through the activities that take place at a lemonade stand. Customer Order Serve Product Collect Payment Produce Product Store Product
- 10. Creating Data Flow Diagrams Example 1. Create a list of activities Also think of the additional activities needed to support the basic activities. Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor
- 11. Creating Data Flow Diagrams Example 1. Create a list of activities Group these activities in some logical fashion, possibly functional areas. Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor
- 12. Creating Data Flow Diagrams Example 2. Construct Context Level DFD (identifies sources and sink) Create a context level diagram identifying the Context Level DFD sources and sinks (users). Sales Forecast Order 0.0 CUSTOMER Lemonade Production Schedule EMPLOYEE Customer Order Product Served System Pay Serve Product Payment Time Worked Collect Payment Received Goods Payment Purchase Order Produce Product Store Product VENDOR Order Raw Materials Pay for Raw Materials Pay for Labor
- 13. Creating Data Flow Diagrams Example 3. Construct Level 0 DFD Create a level 0 diagram (identifies manageable sub processes ) identifying the logical Level 0 DFD subsystems that may exist. 1.0 Sale Customer Order Sales Forecast Customer Order Product Ordered Serve Product Payment Collect Payment 2.0 Production CUSTOMER EMPLOYEE Production Schedule Product Served Produce Product Received Goods Inventory Store Product 3.0 VENDOR Procure- Order Purchase Order Order Raw Materials ment Decisions Pay for Raw Materials Payment Pay Time Worked Pay for Labor 4.0 Payroll
- 14. Creating Data Flow Diagrams Example 4. Construct Level 1- n DFD Create a level 1 (identifies actual data flows and data stores ) decomposing the processes Level 1 DFD in level 0 and identifying CUSTOMER data stores. Customer Order ORDER Request for Forecast Customer Order 1.1 Serve Product Record Collect Payment Order 1.3 Produce Severed Order Sales Produce Product Payment Forecast Sales Forecast Store Product 1.2 Receive PAYMENT Payment Order Raw Materials Pay for Raw Materials Pay for Labor
- 15. Creating Data Flow Diagrams Example 4. Construct Level 1 (continued) Create a level 1 decomposing the processes Level 1 DFD in level 0 and identifying Product Order data stores. ORDER Customer Order 2.1 Serve Quantity Severed Serve Product Product Collect Payment RAW Production MATERIALS Schedule Produce Product 2.2 Store Product Produce Quantity Used Product INVENTORTY Order Raw Materials Production Data Pay for Raw Materials 2.3 Quantity Produced & Store Location Stored Pay for Labor Product
- 16. Creating Data Flow Diagrams Example 4. Construct Level 1 (continued) Create a level 1 decomposing the processes Level 1 DFD in level 0 and identifying Order Decision PURCHASE data stores. 3.1 ORDER Produce Purchase Customer Order Order Quantity On-Hand Serve Product RAW Quantity MATERIALS Collect Payment Received Received Goods 3.2 Produce Product Receive Items Store Product RECEIVED ITEMS Payment Approval Order Raw Materials VENDOR Pay for Raw Materials 3.3 Pay Vendor Pay for Labor Payment
- 17. Creating Data Flow Diagrams Example 4. Construct Level 1 (continued) Create a level 1 decomposing the processes Level 1 DFD in level 0 and identifying Time Worked data stores. 4.1 TIME CARDS Record Time Customer Order Worked Employee ID Serve Product EMPLOYEE Collect Payment Payroll Request 4.2 Unpaid time cards Produce Product Calculate Payroll Store Product PAYROLL Payment Approval Order Raw Materials 4.3 Pay for Raw Materials Pay Employe e PAYMENTS Pay for Labor Payment
- 18. Process Decomposition 1.1 1.2 1.0 Record Receive Sale Order Payment 2.1 2.2 2.3 2.0 Serve Produce Store Production Product Product Product 0.0 Lemonade System 3.1 3.0 3.2 3.3 Produce Procure- Receive Pay Purchase ment Items Vendor Order 4.1 4.3 4.2 4.0 Record Pay Calculate Payroll Time Employe Payroll Worked e Context Level Level 0 Level 1