1. Structured Systems Analysis and Design Methodology Northern College Diploma Philip Bird

2. Information Systems Philip Bird Why Bother? Need to plan and organise – link to life cycle. Help communicate ideas. Get processes (functions) right – Data flow modelling. Get data right – Entity modelling. Cross reference the two – checks built-in. Can be automated.

3. Information Systems Philip Bird Data Flow Modelling Describe the current physical system. Show processes together with data flows between them. Show data stores. Use these to discuss problems with users and help identify requirements for new system.

4. Information Systems Philip Bird Check stock availability Order Product Customer Copy order Order Stock level

5. Information Systems Philip Bird Entity Modelling Things the system needs to store data about Physical – cars, products People – customers, employees Abstractions – order, invoice, booking Each entity has a unique identifier – key attribute/field. Entities linked via relationships.

6. Information Systems Philip Bird One to One 1:1 Woman Man Is the husband of Is married to

7. Information Systems Philip Bird One to Many 1:N Tutor Student Has Is allocated to

8. Information Systems Philip Bird Many to Many M:N Actor Film Has Appears in Actor Film Role

9. Information Systems Philip Bird Entity Attributes Employee ° Employee number Name Address Tax code NI number Pay to date Tax to date ° Key field

10. Information Systems Philip Bird An Example – Hire Car Booking Customer Booking Car Service Mechanic Customer#, Name, Address, Tel Customer#, Date, Car reg, Duration Car reg, Make, Model, Type, Seats, Cost Date, Mileage, Description, Mechanic Name, Qualifications

11. Information Systems Philip Bird Entity Life Histories Describes the entity over time. Check to see there are no missing processes. Are there processes to create, update and delete the entity? Produce diagram that serves as an initial program design.

12. Information Systems Philip Bird ELH For Appointment Entity Appt Make Appt Change Appt VisitNew Year Has Appt No Appt * ºº º = Alternative * = Repetition Where in the DFD is there a process to change an appointment?