structured systems analysis and design methodology
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Structured Systems Analysis and Design Methodology
Northern College DiplomaPhilip Bird
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.
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
Check stockavailability
Order
Product
Customer
Copy order
Order
Order
Order
Stock level
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.
Information Systems
Philip Bird
One to One 1:1
Woman
Man
Is the husband of
Is married to
Information Systems
Philip Bird
One to Many 1:N
Tutor
Student
Has
Is allocated to
Information Systems
Philip Bird
Many to Many M:N
Actor
Film
Has
Appears in
Actor
Film
Role
Information Systems
Philip Bird
Entity Attributes
Employee
° Employee numberName
AddressTax code
NI numberPay to dateTax to date
° Key field
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
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.
Information Systems
Philip Bird
ELH For Appointment Entity
Appt
MakeAppt
ChangeAppt
Visit New Year
HasAppt
NoAppt
*
º ºº = Alternative
* = Repetition
Where in the DFD is there a process to change an appointment?
Where in the DFD is there a process to change an appointment?