1. 3/5/2009Computer systems1 Using Data flow Diagrams Computer System: 1. Input 2. Data Processing 3. Output

2. 3/5/2009Computer systems2 Data Flow Diagram Categorized as : n Logical DFD – focuses on the business – how the business operates – current system n Physical DFD – how the system to be implemented – including n hardware n software n files

3. 3/5/2009Computer systems3 Advantages n Freedom from committing too early. n Understanding of the interrelatedness n Communicating to users n Analysis the necessary data and processes

4. 3/5/2009Computer systems4 Convention Symbols There are four basic symbols: 1. Entity 2. Data flow 3. Process 4. Data store D2

5. 3/5/2009Computer systems5 Example Entity Data flow Process Data store Student 2.1 Create Student Record New Student Information D3 Student Master

6. 3/5/2009Computer systems6 Developing DFD n Creating the context diagram n Drawing diagram 0 n Creating child diagrams

7. 3/5/2009Computer systems7 Context Diagram 0 System Name Entity 1Entity 2Entity 3 Output C Input A Input B

8. 3/5/2009Computer systems8 Diagram 0 4 General Process DDD 3 General Process CCC 2 General Process BBB 1 General Process AAA D2 Data store 2 D1 Data store 1 Input A Input B Data Flow B Data Flow D E1E2E3 Data Flow C Record ARecord E Record A Record E

9. 3/5/2009Computer systems9 Creating Child Diagram n For each process n create diagram n n Number child process with prefix n. – Example: n.1, n.2, n.3, n.4 etc n Child diagram depicts detailed processes n Includes all the inputs and outputs of process n

10. 3/5/2009Computer systems10 Diagram 1 Input A Data Flow B Data Flow C Record A 1.1 General Process AAA 1 1.2 General Process AAA 2 1.4 General Process AAA 4 1.3 General Process AAA 3

11. 3/5/2009Computer systems11 Diagram 2 Input BData Flow B Record E 2.1 General Process BBB 1 2.2 General Process BBB 2 2.3 General Process BBB 3 D3 Data store 3

12. 3/5/2009Computer systems12 Diagram 3 Input B Data Flow D Record A 3.1 General Process CCC 1 3.2 General Process CCC 2 3.3 General Process CCC 1 3.4 General Process CCC 4

13. 3/5/2009Computer systems13 Diagram 4 Data Flow D Record E 4.1 General Process DDD 1 4.1 General Process DDD 1 4.1 General Process DDD 1 D4 Data store 4

14. 3/5/2009Computer systems14 Creating Physical DFD n Convert Logical Data Flow name n To Physical Data Flow name – customer ID bar code – payment in cash – payment by credit card number – report send by mail – report send by email

15. 3/5/2009Computer systems15 Partitioning Data Flow Diagram Examining DFD and divided into collections of: n manual procedures n computer programs For implementation purpose