1. Chris Russell O2.41 02920 41 6431 crussell@cardiffmet.ac.uk
Business Analysis
DFD Levelling
Chris Russell
O2.41
Lecture BA12 DFD Levelling

2. Lecture BA12 DFD Levelling
Session schedule
Business Analysis Schedule
Academic Year
Semester 2
Week
Topic 1
Introduction 2
Investigate situation: rich picture, context diagrams 3
Consider perspectives: types of participation, CATWOE, Power-Interest, Thomas-Kilmann 4
Analyse needs 1: Use Cases 5
Analyse needs 2: structured techniques 6
Define requirements 1a: SSADM 7
Define requirements 1b: SSADM
EASTER 8
Define requirements 2: UML 9
Generic assignment feed-forward and task review 10
Balance good enough software against quality costs; Prioritise requirements 11
Assignment submisison
Lecture BA12 DFD Levelling

3. Activities and Paradigms
Investigate Situation
Consider Perspectives
Analyse Needs
Define Requirements
Socio-technical
Rich picture
CATWOE
Types of participation
Thomas-Kilmann
Power-Interest X
Functional
Level 0 diagram
Structured techniques
DFD, ERM and ELH
Object-Oriented
Context diagram
Use Cases
Class and Sequence diagrams
Lecture BA12 DFD Levelling

4. Lecture BA12 DFD Levelling
Contents
DFD Validation
Review of Publican example
Discussion of Task AD05/AD06
This week, next week
Lecture BA12 DFD Levelling

5. Lecture BA12 DFD Levelling
DFD Validation
Does each process have an appropriate name?
Do the data flows out of a process relate to the data flows in?
Is a process a dead-end for data?
Is a process generating data?
Are all appropriate flows from the preceding level shown?
Can a process be decomposed?
Are all symbols correctly labelled and uniquely referenced?
Do all external entities communicate with a process?
Lecture BA12 DFD Levelling

6. Decomposition Make the process box the system boundary
Draw to the outside of the boundary the sources and recipients of data flows (external entities, or, data stores, or, processes)
Identify and draw the processes at the lower level
Number and name sub processes. Add decimal extension for level. (note the data stores in the process)
Check consistency
The lower level DFD should map onto the higher levels
Review with user departments to ensure that every activity is accounted for
Produce a process description for each elementary process
Lecture BA11 Level 1 DFDs

7. Lecture BA12 DFD Levelling
An example: Publicans
Lecture BA12 DFD Levelling

8. Lecture BA12 DFD Levelling

9. Lecture BA12 DFD Levelling
Publican Level 0
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10. Lecture BA12 DFD Levelling
Publican Level 1
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11. Lecture BA12 DFD Levelling
Publican Level 2 for Process 1
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12. Lecture BA12 DFD Levelling
Publican Level 2 for Process 2
Lecture BA12 DFD Levelling

13. Lecture BA12 DFD Levelling
Old Krate's is a travel agency specialising in exotic holidays. It holds lists of hotels and charter flights, and creates bespoke holidays for clients. Bookings are made either through an OK agent, or by direct approach from clients.
When a client/agent makes an approach, the reservations clerk selects appropriate flight details and hotel details for the customer and makes a provisional booking. The details are entered on the Provisional Booking File.
The customer must confirm the booking within 3 days, by sending a deposit of 10% of the holiday cost. On receipt of the deposit, Reservations close the Provisional Booking and add the details to the Full Booking file.
Four weeks before the flight is due, Accounts send an Invoice to the client for the balance. Accounts notify Customer Services when the balance is received, and Customer Services then send tickets and joining instructions.
Reminders are sent to customers 3 weeks and one week before departure. Although the company insists that payment is made at least one week before departure, it has been known that payment has been made and tickets received on the morning of the flight.
At the end of each month, commission of 15% is paid to any agents responsible for holidays commencing during that month.
Lecture BA12 DFD Levelling

14. Lecture BA12 DFD Levelling
TAD05 - Sources & Recipients
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15. Lecture BA12 DFD Levelling
TAD05 - Context Diagram
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16. Lecture BA12 DFD Levelling
Old Krate’s
Level 1
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17. Lecture BA12 DFD Levelling
Old Krate’s
Decomposition of Process 1
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18. Lecture BA12 DFD Levelling
With only 1 process why break it down?
Lecture BA12 DFD Levelling

19. Lecture BA12 DFD Levelling
Old Krate’s
Decomposition of Process 3
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20. Lecture BA12 DFD Levelling
This week, next week
The task BAT07 is available under Module Documents in BlackBoard
Work on this in your next seminar
Lecture BA12 DFD Levelling