1. Context and Data Flow Diagrams
Activity presented by
Coral Shand
March 2012

2. Scenario
The Car Club has many enthusiastic members. Prospective members can join the club by sending in a membership form along with $10. A planning committee decides on new activities for the coming month and these are passed on to members in a monthly newsletter. Information about all activities past and present are stored for future use. Members also receive reminder letters when their membership is due for renewal.

3. CONTEXT DIAGRAM
Prospective
Member
The Car
Club
Planning
Committee
Member

4. Information in the scenario
Name the data flows
Membership form
 New member details
Planned activities
 Planned activities
Monthly newsletter
 Newsletter
Membership renewal
 Renewal reminder

5. External Entity
Data flow IN
(into the system)
Data flow OUT
(out of the system)
Prospective member
New member details
Member
Newsletter
Renewal reminder
Planning committee
Planned activities

6. CONTEXT DIAGRAM
Prospective
Member
Planning
Committee
New member details
The Car
Club
Planned
activities
Newsletter
Renewal
Reminder
Member

7. Data flow arrows in Context Diagram
Processes for Data Flow Diagram
 New member details
 Add new member
 Newsletter
 Add planned activities
 Renewal Reminder
 Create newsletter
 Planned Activities
 Create renewal reminder

8. DATA FLOW DIAGRAM Prospective Member Planning Member Committee
Create newsletter
Add new member
Create renewal reminder
Add planned activities
Planning
Committee
Member

9. Members
Activities

10. Prospective Member DATA FLOW DIAGRAM Activities Members Planning
Create newsletter
Add new member
Activities
Members
Create renewal reminder
Add planned activities
Planning
Committee
Member

11. Prospective Member DATA FLOW DIAGRAM Activities Members Planning
Create newsletter
Add new member
New member details
Member details
Activities
Members
Create renewal reminder
Add planned activities
Member details
Renewal
reminder
Planning
Committee
Member

12. DATA FLOW DIAGRAM Prospective Member Activities Members Planning
Create newsletter
Member details
Updated
activities
Add new member
New member details
Activities
Updated
activities
Member details
Members
Add planned activities
Create renewal reminder
Member details
Planned
activities
Renewal
reminder
Newsletter
Planning
Committee
Member

13. TEN RULES An external entity must be an intelligence.
Data flows are labelled with adjective-noun.
Processes are named with a verb-noun.
A data flow arrow coming from a process cannot have the same name as a data flow arrow going into that process.
Processes and data stores must have at least one data flow arrow in and one out.

14. A data store cannot link directly to another data store
A data store cannot link directly to another data store. An external entity cannot link directly to another external entity.
Data flows from external entity may keep the same name. Data flowing to and from a data store must have the same name.
Events at same time are one event.
Data flow arrows should not cross each other.
Do not use words ‘data’ or ‘process’ in label names.