Structured Systems Analysis and Design Methodology Northern College

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

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

X-Ray Example I have a problem X-Ray Request GP Patient What’s the result? Meet Appt Request Appt Report X-Ray/History Consultant X-Ray Dept Report System Boundary Information Systems Philip Bird

X-Ray L 1 DFD Appointment 1 X-Ray Dept Appt Card Appt Request Take X-Ray/History Report 2 Information Systems Patient Consultant Produce Report GP Philip Bird

Scenario Patient – Mark Twain Visits the GP with a pain in the middle finger, left hand. (Lives at 14 Sheffield Road, Deepvale) Makes a hospital appointment, (16 th December) and attends the hospital appointment. Revisits the GP to gets the results. GP – Stig Mc. Nasty Fills in an X-Ray Request form for the Patient. (Area to investigate is “Index finger, left hand”) On receipt of the Report from the hospital they request the Patient to make a follow up visit to get the results. Information Systems Records Clerk – Chaka Khan Takes the X-Ray Request and uses this to find old, historical X-Rays and Reports for that Patient. Appends new X-Rays to the historical records and sends them, together with the copy of the X-Ray Request , to the Consultant. Files away the historical records and the new Report from the Consultant. Office Assistant – Bart Simpson Takes the X-Ray Request , finds the patient number from the Patients Record Card file and adds it to the X-Ray Request then files the X-Ray Request away. Takes the Appointment Card , finds the patient number and uses this to retrieve the X-Ray Request. Makes a copy of the X-Ray Request and passes one copy to the Radiographer and the other to the Records Clerk. Radiographer – Gaynor Glow Receptionist – Mae Pang Completes an Appointment Card for the patient at the Radiology clinic and makes an appointment in the Diary. (16 th December). Passes the X-Ray Request to the Office Assistant. When the Patient attends the appointment the Appointment Card is taken and checked in the Diary. The Patient is sent to the waiting room while the Appointment Card is passed to the Office Assistant. Consultant – Don Waters Examines the new X-Rays, checks the X-Ray history and dictates the new Report diagnosing the findings. One copy of the Report goes back to the X-Ray Department with the historical records and one copy goes to the GP. Collects the next X-Ray Request from the pending file, calls the Patient from the waiting room and takes the X-Ray. Passes the X-Ray to the Records Clerk. Philip Bird

X-Ray L 2 DFD Consultant X-Ray Dept X-Ray/History Report Put in In Tray Out Tray View & Dictate Diagnosis History Write Report Send to X-Ray Dept GP Report Copy Report Information Systems Send to GP Report Philip Bird

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

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

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

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

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

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

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