1. Day 4 – Process Modeling: Leveling DFDs
Today’s Tools
More on DFDs
Leveling DFDs
Exercise 5 – in class
Introduce TA’s

2. Day 4 – Process Modeling: Leveling DFDs
Today’s Tools
More on Process Models
Leveling DFDs
Exercise 5 – in class
Introduce TAs

3. DFD diagrams Context Diagram Fig-0 Diagram
A simplified data flow diagram (DFD) of the scope of an organizational system that shows the system boundaries, external entities that interact with the system and the major information flows between the entities and the system
Fig-0 Diagram
A data flow diagram (DFD) that represents a system’s major processes, data flows and data stores at a high level of detail. It is decomposable.
The chart on the right shows the relationship between diagrams
Now I’m going to focus on the figure 0 and later in the class discuss the context diagram.

4. Celis Brewery Example of a Context Diagram
This high level DFD shows the system and its environment.
Environmental elements in squares
One unnumbered process bubble (name of system)
Order Requisitions
Orders
Order Confirmation
Suppliers
Distributors
Order Cancellations
Supplies
Celis
Brewery
ITS/IPS
Shipment Date Changes
Summary of Removals
Note: these can be complex if there are many data flows to and from many external entities.
This is the Celis Inventory Tracking System and Inventory Projection System, begun by a 374 team in spring 1998.
Critical Levels Report
Recipients
Of Free Beer
Beer Donation letters
Management
Order Log Report
Inventory Log Report
Thank You Letters
Inventory Discrepancy Report
Arrows show data flow to and from the environmental elements.

5. Data Flow Diagramming Rules
Inputs to a process are always different than outputs
Processes must have both an input and an output
Objects always have a unique name
In order to keep the diagram uncluttered, you can repeat external entities & data stores on a diagram
No more than seven processes on one diagram
A process has a verb phrase label
Data only flows in one direction at a time
Data flows are nouns
Data must be transformed by a process (cannot be moved directly from one store to another or from an external entity to a data store).
Data store has a noun phrase label

6. The Data Flow Diagram—Figure 0
Standard rules apply however,
It is OK to have no actors on Figure 0, if appropriate
Remember: No more than seven (7) processes on one diagram
Use multiple levels to describe what is going on

7. Overview of a Leveled DFD
Context Diagram
Drill down to show more detailed processes, data flows, and data stores.
Fig 0 Diagram
Level 1
Fig 4 Diagram
Level 2
Fig 4.5 Diagram

8. ASTA DFDs
How many external elements interface with the Proposed Skill Set System?
How many data flows are going to and from the system?

9. Compare the two levels

10. Compare Figure 0 and Figure 3
# 3.1
Level 1 dfd
# 3.2
Note numbering: Process 3 becomes the drilled down DFD called Figure 3 (Level 1)
The process bubbles for Figure 3 are numbered 3.1, 3.2, etc.
You are required to create a Context Diagram for Group Project #1 as well as Level 0, Level 1, and Level 2 DFDs.
For your client project you should create a context diagram & Figure 0 DFD for the 2nd meeting. You’ll need to ask the right questions at the first meeting to be able to create the diagrams.

11. Celis Example -- Figure 0 DFD
This Figure 0 shows 3 evolutions of the Celis system. This is an excellent way to communicate scope and be clear that you heard the client’s request.
Process 1 was completed by a team in spring 1998.
Process 3 was also completed by the spring 1998 team, but the COO at Celis was unhappy with it.
This highlighted in blue to indicate that the spring 1999 team will redo this portion of the system – Process 3 is their project scope for the semester.
Process 2 was something that the COO requested, but the team did not think they could complete this functionality. They recommended that this functionality be added by a fall 1999 team.

12. Celis Figure 3 DFD Reminder: This is a Level 1 DFD.
Note that process & data store numbers read left to right and top to bottom.
Figure 3 is a drill down to show the details of the process that is included in the project scope.
This figure 3 is close to too complicated – it has 6 process bubbles and the max is 7.
It would have been more complex, but the team collapsed some of the detail into Process 3.2 and then showed that detail on a leveled DFD.

13. Celis Figure 3 DFD
Figure 3 is a drill down to show the details of the process that is included in the project scope.
This figure 3 is close to too complicated – it has 6 process bubbles and the max is 7.
It would have been more complex, but the team collapsed some of the detail into Process 3.2 and then showed that detail on a leveled DFD.

14. Celis fig 3.2 DFD -- drill down detail
Drill down for one of the processes from Figure 3
Notice that DFDs read from left to right, and top to bottom, like a written page.

15. Celis fig 3.2 DFD -- drill down detail
This is a Level 2 DFD.
S10
S11
Drill down for one of the processes from Figure 3 S6
The Data Store #’s should match the higher level DFDs.

16. DFD Summary
The data flow diagram (DFD) models the processes of an information system
DFDs consist of processes, external entities, data stores, and data flows
DFD modeling begins with the Context Diagram, which depicts the entire system in a single process symbol surrounded by external entities

17. DFD Summary
The first-level DFD (Figure 0) shows the major functional components of the system as processes, connected by data flows to external entities, data stores, and other processes
As needed, successively more detailed levels are developed to promote complete understanding of the system
As you drill down, figures are named by the Process, not the level.

18. Reality & DFD creation DFDs are usually created from messy notes.
What you think initially might be the best organization of the process usually isn’t what will be the final version.
So, assume you will start with a messy first draft and then clean up the process by leveling the DFDs:
Figuring out what the major processes are for the Figure 0 DFD
and then creating the lower level DFDs with the details
TIP: DFD Summary and Rules on Resources page

19. Caution about Group Project DFDs
Unlike the Client Project, you read text to create your DFDs.
Instead of leaving the leveling process (the drill down process) wide open, the text was written with a sense of what the main processes are. The assignment is very specific.
Best approach?
Maybe create a messy detail DFD, then look back at the process bubbles listed in the requirements.
Or maybe start with the process bubbles in the requirements and figure out what needs to be added.
No one “right” way…

20. Reminders & Tips Send email to both professors for faster response
For Next class – bring your laptop

21. Group Project #1 Do not bind your report
Put team number in footer w/page number
Peer evaluations are due after the project is submitted
Don’t give all 10’s.
You have a chance to explain, so if you feel this was the Best Group In The World, you can tell us.
It does not improve your grade
It makes you look bad
CONFIDENTIAL
No one will ever see it except your professors
We look at your peer evals throughout all groups