Structured Systems Analysis and Design Methodology

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Structured Systems Analysis and Design Methodology

• Northern College Diploma
• Philip Bird

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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.

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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.

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Customer
Order
Stock level
Order
Order
Order
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X-Ray Example
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X-Ray L1 DFD
Appointment
Appt Card
Appt Request
X-Ray/History
Report
Report
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Scenario
Receptionist Mae Pang Completes an Appointment
Card for the patient at the Radiology clinic and
makes an appointment in the Diary. (16th
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.
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.
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, (16th December) and attends the
hospital appointment. Revisits the GP to gets the
results.
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.
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.
GP Stig McNasty 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.
Radiographer Gaynor Glow 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.
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X-Ray L2 DFD Consultant
X-Ray/History
History
Report
History
Report
Report
Report
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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.

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One to One 11
Woman
Is the husband of
Is married to
Man
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One to Many 1N
Tutor
Has
Is allocated to
Student
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Many to Many MN
Actor
Film
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Entity Attributes
Employee number Name Address Tax code NI
number Pay to date Tax to date
Employee
Key field
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An Example Hire Car Booking
Customer
Customer, Name, Address, Tel
Customer, Date, Car reg, Duration
Car reg, Make, Model, Type, Seats, Cost
Date, Mileage, Description, Mechanic
Name, Qualifications
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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.

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ELH For Appointment Entity
Appt
Make Appt
Change Appt
Visit
New Year

Where in the DFD is there a process to change an
appointment?
º
º
Has Appt
No Appt
º Alternative
Repetition