03 - “The Tool”
Have read chapter 5
….BSD00_Context (file)
….BDS00_System (file)
……..BDS00P00_Sales_Service (file)
….……..BDS0000P00_In_Store (file)
…………BSD0000P01_Online_Sales (file)
…………….BSD000001P02_Process_Sale (file)
….Rules_Process (file)
The system level DFD is the first decomposition. Consider the bookstore CONTEXT DFD and look at the
(squared box) process BSD 00 as the roof of your house. Now consider removing the roof from the
process box and looking inside to find different “rooms” inside. A kitchen, bath, den, and so on. This is
the first decomposition of the project moving towards the many atomic levels that will be built. Instead of
rooms we will find major level processes such as marketing, human resources, sales, and facilities.
Traditionally there are between five and seven system level processes. Think of what department or
processes areas are found within the organization. Remember we are only going to model what happens
inside the theoretical building.
The system DFD is also labelled NAME 00 as the CONTEXT. Note that the name of the DFD is from the
parent and the children processes are NAME 00 P00, P 01, etc. The next decomposition for the DFD
labelled NAME 00 P 00 will have children named NAME 00 00 P 00, P 01, etc. The decomposition for the
DFD labelled NAME 00 P 03 will have children named NAME 00 03 P 00, P 01, etc.
Atomic level process - The last (bottom) process of the firm decomposition. Consider a checkout lane at
a grocery store. You give the item to the clerk to scan, it reads the UPC, finds the inventory data,
identifies the price and reduces the inventory level, transfers the charge to your receipt, and moved to the
atomic level of payment.
We use the term decomposed because we start the analysis for the top down. The first process (Context)
represents the entire firm, think of it as the wall around the store. Like the building around a CVS
pharmacy that encloses processes like non-regulated inventory, controlled substances, sales,
maintenance, and time clocks. The space includes everything to make the firm functional. A fast food
restaurant, a shoe store, or a dentist office would also have the same areas or departments.
In the example of a restaurant you may have customers that can purchase alcohol and those who cannot,
thus creating a different entity. A grill operator may not run a cash register, but a manger could do both.
When a manager changes functions between the grill and the cash register he/she assumes that new
entity class.
What must be solidified at this point is accurately defining all of the entities. Each entity has a unique
label and a specific definition or set of constraints. At a day care a teacher may also be a bus driver for
the students. But when he/she drives the bus a different set of business rules apply such as a
commercial driver’s license. So that individual changes the entity class they are functioning in. At this
point the rules of decomposition should be reviewed.
To this point the student context and system DFDs look very similar. From this point forward each project
will decompose into unique series of “roots” ending in atomic level processes.
Take one major system level process (such as facilities or human resources) and create the first
decomposition DFD. There will be a number of processes on this new DFD (and none will be at the
atomic level). Consider human resources where you have the “children” of staffing, training, and payroll.
All of these logically have children of their own such as staffing may have hiring and termination.
Termination may have voluntary and none voluntary release.
With the above DFD you have started a new “leg” of decomposition, where each “root” will end at various
lengths. Again you will need to define these new processes by their name and number in the data
dictionary. Note that all processes need to be defined in the data dictionary.
As each process needs at least one data store consider the logic of what types of data will be needed to
complete the future children (processes). As an example hiring (at a lower level of decomposition) may
have the need for external data along with personnel and organizational data when advertising for a job
with a newspaper.
In the example (BSD 00 P 00_Sales_Service) the data store Cust_Data is only attached to the process
ONLINE SALE.
This project is only looking at what is (modelling exactly how processes functions within the organization).
In the marketplace this analysis is normally already available in different forms (job descriptions, flow of
documentation, etc.). The value of modelling really is attached to what functional changes can be made
to accomplish the identified atomic level processes and what structure is needed to do so.
Consider an ATM cash machine and how it replicates a defined set atomic level activities that were
previously only available at the counter from a clerk. You cannot negotiate a loan or break a large bill, but
these processes are not included in the ATM business model. Another example would be the changes in
the auto insurance industry. What did Progressive have to change to not be State Farm?
Considering the major process you have identified, what are the issue associated with collapsing links of
the value chain, eliminating duplication, or removing none productive steps.
General Application Rules Chart:
NAME
SYMBOL
RULES
LABELS/NUMBER
REQUIRED ENTRY
Process
Each process is unique.
DFDs decompose on
processes.
Each with unique
name and number.
Diagram and
Description.
Stored Data
Can be nested or reused.
Represent the mass logical
data stores (MLOG/LOG).
Each with unique
name.
Description and
MLOG/LOG entry.
Entity
Must be reused.
Each with unique
Entities represent teams of
name.
individuals/function providers.
Description.
Data flow
Each data flow is unique.
Nested, but not modeled.
Each line has two
Labels. One way linear
relationship are rare!
Flow table for DFDs
with any ATOMIC
PROCESSES.
Each with unique
name. No label
required for linear
relationship.
HOW TO GUIDE:
Your project will NOT require SV/MV designations. Below is an example of a M_LOG
composition:
M_LOG CABINET
M_LOG_BACKPACK
M_LOG_ CHECK_BOOK
M_LOG_WALLET
LOG_DRIVER_LIC
NAME
SSIN
DOB
LIC_NUMBER
EXPIRE_DATE
LOG_SHELL_CREDIT_CARD
NAME
ACCT_NUMBER
EXPIRE_DATE
M_LOG_ORGANIZER_BOOK
D2L_ACCT_NUMBER
D2L_PASSWORD
LOG_ADDRESS_BOOK
NAMES
HOME_ADDRESS
WORK_ADRESS
HOME_PHONE_NUMBER
WORK_PHONE_NUMBER
JH0000P01
1
2
3
4
5
6
7
8
9
10
11
12
Payment Services
To the process
From the process
rec_norm_emp_log_computer
rec_cont_emp_log_computer
rec_emp_reg_data
mgnt_reg_supervise
req_norm_emp_pmt
req_cont_emp_pmt
req_mgnt_pmt
validate_credit_Check_pmt
send_Pmt_credit_data
sub_order_pmt_data
rec_tax_data
req_reg_cash_data
<EOF>(03A150424)
req_norm_emp_log_computer
req_cont_emp_log_computer
req_emp_reg_data
mgnt_correct_supervise
rec_norm_emp_pmt
rec_cont_emp_pmt
update_mgnt_pmt
validate_credit_Check_acct
rec_decision_credit_data
rev_order_pmt_data
rev_tax_data
rec_reg_change_cash_data