1. Events to Data Flows to Data Dictionaries System Analysis & Design

2. Library Video Check Out System Example n The essential requirements for the tape check out system are described in terms of events. – –First, a patron will want to check out tapes and then later return them. – –Sometimes a patron will neglect to return a tape by the due date and needs a reminder. – –Occasionally the tape will not be returned at all and should be considered lost. – –New tapes will be received by the library from time to time. – –Library management will want information about tape check out activity about once a month.

3. Event Table

4. Context Diagram

5. Data Flow Fragments Patron wants to check out tape Patron returns tape

6. Data Flow Fragments Tape is overdue Overdue tape is assumed lost

7. Data Flow Fragments New tape is received Time to produce monthly tape activity report

8. Diagram 0 Event Partitioned Diagram

9. Data Dictionary Starting A Data Dictionary n Useful to examine one data flow fragment at a time and identify data inputs and outputs – –Consider… – –Looking at each data flow we can attempt to identify data structures and from that, data elements.

10. Data Dictionary Starting A Data Dictionary n CHECK-OUT-REQUEST –CUSTOMER-DETAILS =CUST–NAME+CUST-ADDRESS+CUST-ID n CHECK-OUT-REQUEST

11. Data Dictionary Data Elements Data Element Description Name: CUSTOMER-ID Alias: Type & Length: Output Format: Default Value: Source:Security: Responsible User: Description: Description: A number that uniquely identifies a patron

12. Data Dictionary Data Flow Data Flow Description Name: CHECK-OUT-REQUEST Alias:Origin:Destination: Description: Description: Is composed of a customer identification number and a tape identification number CHECK-OUT-REQUEST =

13. Data Dictionary Data Flow Data Store Description Name: TAPE-FILE Alias: Input data flows: Output data flows: Description: Description: Contains an unbounded sequence of tape records where each record is a composite of tape number and tape title. The tape number will be used to access the file. TAPE-FILE =

14. Data Dictionary Data Entity Data Entity Description Name: PATRON Alias: Input data flows: Output data flows: Description: Description: The patron is a library member

15. Data Dictionary Data Process Data Process Description Name: CHECK-OUT-TAPE Process Number: 1 Alias: Input data flows: Output data flows: Description: