1. Context Diagram

2. Bound the Problem Identify in-the-large constraints
Identify major data -- in and out
A Context Data Flow Diagram provides a first broad-based cut
© The KTP Company, 2005

3. A Context Data Flow Diagram ...
Is a high-level functional model illustrating basic information flow.
Shows the relationships of external entities, such as processes, data items, data bases, and existing systems, to the proposed system.
Identifies all major input and output data flows of the proposed system, as well as the sources and destinations of these data flows.
At a high-level, it answers the question: “What are we trying to do?”
It lays out the broad scope and outline of the system.
© The KTP Company, 2005

4. Context DFD: An Example
Consider the following example:
A company wants to create an online system that will allow managers, project leaders, and team leaders to reserve meeting rooms at the company’s main campus complex. Here are some salient features for the system:
The system should keep track of all schedulable rooms, contact information for all persons making inquiries or reservations, and of course the current and future reservation schedule.
The person charged with managing room reservations needs a report at the end of the day detailing the next day’s meeting schedule.
The system should allow for cancellation of reservations.
It should an automated reminder message to the reserver two hours prior to any scheduled meeting. 4
© The KTP Company, 2005 4

5. Example Context Data Flow Diagram
Here’s a first draft for a Context Data Flow Diagram for this system.
Group Activity: Critique the diagram and modify it as needed. Are there any additional likely data flows that you can think of which aren’t mentioned here?
Room Data
Employee Data
room_parameters
emp_status
room_data
availability
Proposed
Room
Reservation
System
login_request
reservation
login_conf
Reservation Data
Room
Requester
res_request
cancellation
res_conf
res_denial
cancel_req
room_updates
Reservation Manager
daily_rep
cancel_conf
reminder
System
reminder 5
© The KTP Company, 2005 5

6. Team Activity #3
Consider the proposed Web-based self-service financial services system introduced earlier. Here are the salient features of the system known so far:
The underlying philosophy for the system is one of customer self-service – a new approach for this company.
The system should provide customers direct access to status information appropriate to their current accounts.
The system should provide customers access to their account history with the company.
The system should provide “canned responses for frequently asked questions about investment strategies.
The system should provide an opportunity for customers to pose additional questions (to be responded to later).
With your team, construct a first draft of a Context DFD for this proposed system – one that could be used in a meeting with the project sponsor and other customer representatives to further explore the requirements for the system.
© The KTP Company, 2005

7. Usefulness of the Context DFD
Enhances communication about the proposed system
Can be understood by a variety of stakeholders, including customers
Allows quick explorations of ideas, concepts, and understandings
Helps validate understanding with customers
Easy to modify and re-validate
© The KTP Company, 2005

8. Limitations of Context DFD
Does not attempt to model functionality of the proposed system at a lower level
Not intended to be a detailed description
Does not include control or sequencing information (generally, this should be left to the design phase)
Photo by Anja Ranneberg, taken in Oamaru, New Zealand, where little blue penguins come ashore to breed at night.
© The KTP Company, 2005

9. Team Activity #4
Recall the example project to create an online system that will allow managers, project leaders, and team leaders to reserve meeting rooms at a company’s main campus complex. Here are some salient features for the system:
The system should keep track of all schedulable rooms, contact information for all persons making inquiries or reservations, and of course the current and future reservation schedule.
The person charged with managing room reservations needs a report at the end of the day detailing the next day’s meeting schedule.
The system should allow for cancellation of reservations.
It should an automated reminder message to attendees two hours prior to any scheduled meeting.
© The KTP Company, 2005

10. Team Activity #4 (cont’d)
Here’s our first draft for a Context Data Flow Diagram for this system.
Room Data
Employee Data
room_parameters
emp_status
room_data
availability
Proposed
Room
Reservation
System
login_request
reservation
login_conf
Reservation Data
Room
Requester
res_request
cancellation
res_conf
res_denial
cancel_req
room_updates
Reservation Manager
daily_rep
cancel_conf
reminder
System
reminder 10
© The KTP Company, 2005 10

11. Team Activity #4 (cont’d)
Review the Context DFD we created for this system earlier.
At this level of analysis, can you anticipate elements that might require input from the Design Architect Group?
If so, for each element you identified, explain why you believe the DA Group’s input would be important.
At this level of analysis, can you begin to think about how the eventual system will be tested?
If not why not? If so, can you tentatively identify some components of a Test Plan?
© The KTP Company, 2005