Need an example of the following two diagrams (must use the attached slides as a reference).

Using a modeling tool, build a Context Diagram and a Level 0 DFD for an imaginary car rental system. 

 

Additional references:

FreeTutes. (2011). The procedure for producing a data flow diagram. Retrieved from http://www.freetutes.com/systemanalysis/sa5-procedure-producing-dfd.html

FreeTutes. (2011). An example of a DFD for a system that pays workers. Retrieved from http://www.freetutes.com/systemanalysis/sa5-dfd-system-pays-workers.html

Modern Analyst. (2011). Data flow diagrams with examples and tips. Retrieved from http://www.modernanalyst.com/Resources/Articles/tabid/115/articleType/ArticleView/articleId/2015/Data-Flow-Diagram-with-Examples-Tips.aspx

 

 

DATA FLOW
DIAGRAM
PART 2 Creating Data Flow Diagrams
Creating DFDs is a highly iterative process of
gradual refinement.
General steps:
1. Create a preliminary Context Diagram
2. Identify Use Cases, i.e. the ways in which users
most commonly use the system
3. Create DFD fragments for each use case
4. Create a Level 0 diagram from fragments
5. Decompose to Level 1,2,…
6. Go to step 1 and revise as necessary
7. Validate DFDs with users. Context Diagram Top-level view of IS
A 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
Example: Order system that a company uses to
enter orders and apply payments against a
customer’s balance DFD Rules—Context Diagram
One process, numbered 0. Sources and sinks (external entities) as
squares Main data flows depicted No internal data stores are shown They are inside the system External data stores are shown as external
entities How do you tell the difference between an
internal and external data store? Context
Diagram of
Order
System Level-0 DFD Shows the system’s major processes, data flows,
and data stores at a high level of abstraction
When the Context Diagram is expanded into DFD
level-0, all the connections that flow into and out of
process 0 needs to be retained. Context
Diagram of
Order
System Level-0
DFD of
Order
System Lower-Level Diagrams
Functional Decomposition Balancing Decomposition of DFDs Functional decomposition An iterative process of breaking a system description
down into finer and finer detail Uses a series of increasingly detailed DFDs to
describe an IS Act of going from one single system to many
component processes Repetitive procedure Lowest level is called a primitive DFD Level-N Diagrams A DFD that is the result of n nested decompositions of
a series of subprocesses from a process on a level-0
diagram Balancing DFDs When decomposing a DFD, you must conserve
inputs to and outputs from a process at the next
level of decomposition
Ensures that the input and output data flows of
the parent DFD are maintained on the child DFD
This is called balancing
Example: Hoosier Burgers In Figure 1, notice that there is one input to the
system, the customer order Three outputs: Customer receipt
Food order
Management reports Figure 1
Context diagram of Hoosier Burger’s Food ordering
system Balancing DFDs Example
(Continued)
Notice Figure 2. We have the same inputs
and outputs No new inputs or outputs have been
introduced We can say that the context diagram and
level-0 DFD are balanced Figure 2
Level-0 DFD of Hoosier Burger’s food ordering system Balancing DFDs:
An unbalanced example Figure 3: In context diagram, we have one input to the
system, A and one output, B Level-0 diagram has one additional data flow,
C These DFDs are not balanced Figure 3: An unbalanced set of data
flow diagrams
0 A B
SINK SOURCE (a) Context diagram
A 1.0 SOURCE 1
C
SOURCE 2 2.0 B
SINK (b) Level-0 diagram Balancing DFDs
We can split a data flow into separate data
flows on a lower level diagram (see Figure
4) Balancing leads to four additional
advanced rules Example of data flow splitting
Payment & coupon Payment Coupon x.0 Composite data
flow x.1 x.2 Disaggregated
data flow Advanced Rule for DFD A composite DF on 1 level can be split into component
DF as the next level, but no new data can be added n all
data in the composite must be accounted for in 1 or more
subfollows
The inputs to a process must b sufficient to produce the
outputs from the process
At the lowest level of DFD, new data flows may be added
to represent data that r transmitted under exceptional
condition, these data flows typically represent error
message
To avoid having data flow lines cross each other, u may
repeat data strores or sources/sinks on a DFD. Use an
additional symbol, like a double line on the middle vertical
line of data strore symbol, or a diagonal line in a corner of
a sink/source square to indicate a repeated symbol Strategies for Developing DFDs Top-down strategy Create the high-level diagrams (Context
Diagram), then low-level diagrams (Level-0
diagram), and so on Bottom-up strategy Create the low-level diagrams, then higherlevel diagrams Exercise:
Precision Tools sells a line of high-quality woodworking
tools. When customers place orders on the company’s Web
site, the system checks to see if the items are in stock,
issues a status message to the customer, and generates a
shipping order to the warehouse, which fills the order.
When the order is shipped, the customer is billed. The
system also produces various reports, such as inventory
reports for Accounting. Draw a context diagram for the order system Draw DFD diagram 0 for the order system Identify Entities,Process,Data Stores & Data Flow Entities Processes Customer
Warehouse
Accounting
1.0 Check Status
2.0 Issue Status Messages
3.0 Generate Shipping Order
4.0 Manage Accounts
Receivable
5.0 Produce Reports Data Stores D1 Pending Orders
D2 Accounts Receivable Data Flows Order
In-Stock Request
1.0
Order Data
Status Data
2.0
Status Message
Shipping Order
3.0
Order Data
Invoice
Shipping Confirmation
4.0
Payment
Accounting Data
Accounts Receivable Data
5.0
Order Data
Inventory Reports Context Diagram of Order System Level-0 of
Order
System HOMEWORK (group) Based on the use cases, draw your
project data flow in: Context diagram Level 0-DFD If neccesary, decompose the DFD to the next
level DFDs Put them on your SRS’s document as the
attachment

Attachments:

• 1493168329-103933DFD_Modeling.ppt