Systems Documentation Techniques
Professor Merle Martin
Professor Yan Xiong
College of Business
CSU Sacramento
2/6/023
Agenda
Why Document System
 Data Flow Diagrams
 Flowcharts
 Difference between DFDs and
Flowcharts

Why Document Systems?
User confidence that you understand
system
 Successive refinement of detail down
to programming level
 Ease of Program Maintenance,
System Modification, Reengineering,
and Replacement

Why Document Systems?


Problem Solving
Humans solve complex
problems by
breaking them into smaller and
smaller modules
until they fit into the human mind
solving the modular sub-problems
aggregating small solutions
into total solution
Agenda
Why Document Accounting
Information Systems
 Data Flow Diagrams (DFDs)
 Flowcharts
 Difference between DFD

Data Flow Diagrams
Data flow diagram (DFD)
graphically describes flow
of data within any system
 Used to document existing systems
and to plan and design new ones
 No ideal way to develop a DFD
 judgment within standard rules

Data Flow Diagrams





DFD composed of only four elements:
Data sources and destinations: External Entities
 Another organization/organization unit which
exchanges data with the focal system
 A person who interacts with the system
(customer of a banking system)
 Another information system
Data Flows
Processes
Data Stores: Temporary or permanent repository
of data
DFD Symbols
INPUT
PROCESS
External
Entity
Source
Data
Data
Process
Flow
Flow
Data
Flow
OUTPUT
Data
Store
External
Entity
Sink
DFD Symbols
Customer
Source
1.1
Process
Payment
Payment
deposit
Remittance data
Customer
File
Bank
Sink
Data Flow Diagrams Explosion
Data flow diagrams
subdivided into successively
lower levels in order to provide
increasing amounts of detail
 This decomposition process is
called “explosion”

Data Flow Diagram Explosion
Context Level
 Ist Level Explosion
 2nd Level Explosion
 Succeeding levels as necessary
 Until reach primitive level
 Ready to code

Context Diagram



Includes only
External Entities
Data Flows
All elements included on Context
Diagram must be included
somewhere on lower level diagrams
Data stores rarely included!
Context Diagram
Why discourage Data Stores on
Context Diagram?
 Author includes them
 Context Diagram shows interaction
of your system with outside world
 Data Stores are INSIDE your system,
not in outside world

Purchase
Inventory Requisition
System
Order
Entry
System
Special
Order
Purchase
Order
0
Purchasing
Purchase
Order
Notification
Context Diagram
Vendor
Receiving
System
1st Level Explosion
Also includes all data
flows and external entities
 Now data stores are added
 Excellent means of confirming
understanding of system between
analyst and client
 Each process will be exploded into
lower level DFDs

Ist Level Explosion
Inventory
Purchase
Requisition
P.Order
1
Edit
Order
Approved
2 Order
Set Ship
Mode
Order
Entry
Vendor
Inventory
Vendor
Draft P.O
P.O. Copy
3
Prepare
P.O.
Problem
Orders
P.O.Notification
Receiving
2nd and Succeeding
Levels

Must be consistent with
parent DFD
 Same external entities
 Same data stores
 Same data flows
2nd Level Explosion
(Process 1)
Inventory
Order
Entry
Log-in
#s
Purchase
Requisition
1.1
Log-in
Order
Logged-in
1.2 Order
Edit
Order
Inventory
Problem
Orders
Edited
Order
1.3
Approve
Order
Approved
Order
Process
2.1
DFD Rules -- Process
A. No process can have only outputs (a
miracle)
B. No process can have only inputs (a
black hole)
C. Verb phrase labels
DFD Rules -- Data Store
D. Data cannot move directly from one data store
to another data store -- it must be moved by a
process.
E. Data cannot move directly from an outside
source to a data store -- it must be moved by a
process.
F. Data cannot move directly to an outside sink
from a data store -- it must be moved by a
process.
G. Noun phrase label
DFD Rules -- Source / Sink
H.
I.
Data cannot move directly from a
source to a sink. It must be moved
by a process.
Noun phrase label
DFD Rules -- Data Flow
J. A data flow has only one direction of flow
between symbols; a data flow may flow in
both directions to and from a data store
(usually two symbols)
K. A fork in a data flow means that exactly
the same data goes to two different
processes or data stores.
DFD Rules -- Data Flow
L. A data flow cannot go directly back
to the same process it leaves
M. A data flow to a data store means
update (delete or change)
N. A data flow from a data store means
retrieve or use
O.Noun phrase label
Other DFD Issues

Two additional guidelines
 Inputs
to a process are different from outputs
of that process
 Every process in a DFD has a unique name
Exercise
Draw a Context Diagram and a 1st level explosion
Current System Description for the payroll system at No-Wear Products.

Time data are recorded in each department using time cards and
clocks.

The time data are sent to the payroll by different departments.

Payroll clerks review the time data for their completeness.

Human resources send the payroll data on personnel changes, such
as increases in pay rates and new employees.

Payroll clerks update the payroll file based on these changes.

At the end of the period, payroll clerks enter the time card data into
the payroll file for processing. The payroll supervisor reviews the file
and makes necessary corrections.

Payroll clerks send the direct payments to the bank and also the
direct deposit slips to the departments.
Agenda
Why Document Accounting
Information Systems
 Data Flow Diagrams
 Flowchart
 Difference between DFD and
Flowchart

Flowcharts


A flowchart is an analytical technique
used to describe some aspect of an
information system in a clear,
concise, and logical manner.
Flowcharts use a standard set of
symbols to pictorially describe
transaction processing procedures.
Flowchart Symbols

Flowcharting symbols can be divided
into the following four categories:
1 Input/output symbols
2 Processing symbols
3 Storage symbols
4 Flow and miscellaneous symbols
Flowcharting Symbols:
Input Output Symbols
Symbol
Name
Document
Online keying
Display
Input/output;
Journal/ledger
Flowchart Symbols:
Processing symbols
Symbol
Name
Manual operations
Computer processing
Auxiliary operation
Flowchart Symbols:
Storage Symbols
Symbol
Name
Magnetic disk
Magnetic tape
Flowchart Symbols: Flow and
miscellaneous Symbols
Symbol
Name
Document or processing flow
On-page connector
Off-page connector
Terminal
Decision
What are Document Flowcharts?



A document flowchart illustrates the flow
of documents and information between
areas of responsibility within an
organization.
A document flowchart is particularly
useful in analyzing the adequacy of
control procedures.
Flowcharts that describe and evaluate
internal controls are often referred to as
internal control flowcharts.
What are Computer
System Flowcharts?



System flowcharts depict the
relationship among the input,
processing, and output of an AIS.
A system flowchart begins by
identifying both the inputs that enter
the system and their origins.
The input is followed by the
processing portion of the flowchart.
What are Computer
System Flowcharts?


The resulting new information is the
output component.
System flowcharts are an important
tool of system analysis, design, and
evaluation.
What are Computer
System Flowcharts?
Input
Storage
Process
Output
What are Program Flowcharts?



A program flowchart describes the
specific logic to perform a process
shown on a systems flowchart.
A flow line connects the symbols and
indicates the sequence of operations.
The processing symbol represents a
data movement or arithmetic
calculation.
What are Program Flowcharts?
Input data
If a condition is met
Yes
Perform calculation
Update record
No
What are Program Flowcharts?



The input/output symbol represents either
reading of input or writing of output.
The decision symbol represents a
comparison of one or more variables and
the transfer of flow to alternative logic
paths.
All points where the flow begins or ends
are represented by the terminal symbol.
Flowchart for Processing
Credit Orders
Start
Enter
sales
order
Approved
for credit?
No
Reject
order
No
Backorder
Yes
Inventory
available?
Yes
Fill order
Stop
Example-Flowcharts

The Dewey Construction Company processes its
payroll transactions to update both its payroll master
file and its work-in-process master file in the same
computer run. Both the payroll master file and the
work-in-process master file are maintained on disk and
accessed directly.
Data to be input to this system are keyed onto a tape
using a key-to-tape encoder. This tape is then
processed to update the files. This processing run also
produces a payroll register on magnetic tape,
employee paychecks and earnings statements, and a
printed report listing error transactions and summary
information.
Prepare a system flowchart of the process described.
Job Time
Tickets
Key to
Tape
Encodings
Job Time
Records
Tape
Payroll
Master
File
Work in
Process
Master
File
Payroll
Processing
System
Earnings
Statement
Payroll
Register
Paycheck
Error
Transactions
and Summary
Agenda
Why Document Accounting
Information Systems
 Data Flow Diagrams
 Flowchart
 Difference between DFD and
Flowchart

Differences Between DFDs and
Flowcharts


DFDs emphasize the flow of data and
what is happening in a system,
whereas a flowchart emphasizes the
flow of documents or records
containing data.
A DFD represents the logical flow of
data, whereas a flowchart represents
the physical flow of data.
Differences Between DFDs and
Flowcharts


Flowcharts are used primarily to
document existing systems.
DFDs, in contrast, are primarily used
in the design of new systems and do
not concern themselves with the
physical devices used to process,
store, and transform data.