systems documentation: systems flowchart & data flow diagram

I S 6 3 0 : A c c o u n t i n g I n f o r m a t i o n S y s t e m s h t t p : / / w w w. c s u n . e d u / ~ d n 5 8 4 1 2 / I S 6 3 0 / I S 6 3 0 _ F 1 2 . h t m

Systems Documentation: Systems Flowchart & Data Flow Diagram

Lecture 1

System Documentation

System Flowcharts present a comprehensive picture

of the management, operations, information

systems, and process controls embodied in business

processes.

Data Flow diagrams (DFD) portray a business

process activities, stores of data, and flows of data

among those elements.

IS 630 : Lecture 3 2

Systems Flowcharts

Systems Flowchart: a graphical representation of a

business process, including information processes

(inputs, data processing, data storage, and

outputs), as well as the related operations processes

(people, equipment, organization, and work

activities).

( Also known as “process flowcharts” and “business

process flowcharts.”)


Standard Flowcharting Symbols


Common System Flowcharting Routines

Enter document into

computer via keyboard,

edit input, record input.

(Note that columns are

set up to communicate

the flow of activities

between processing

entities.)


Common System Flowcharting Routines …

User queries the

computer


Common System Flowcharting Routines . . .

Update sequential data

store



Preparation and then

manual reconciliation of

control totals.



Key and rekey to verify

inputs



Enter document into

computer using a

scanner



Enter document into

computer using

scanner and then

manual keying


Preparing Systems Flowcharts

1. Divide the flowchart into columns (areas of

responsibilities): one column for each internal

entity and one for each external entity. Label

each column.

2. Flowchart columns should be laid out so that the

flowchart activities flow from left to right. But,

minimize crossed lines and connectors.

3. Flowchart logic should flow from top to bottom

and from left to right. For clarity, put arrows on all

flow lines.


Preparing Systems Flowcharts . . .

4. Keep the flowchart on one page, if possible. With

multiple pages use off-page connectors.

5. Within each column, there must be at least one

manual process, keying operation, or data store

between documents. Do not directly connect

documents within the same column.

6. When crossing organizational lines (one column to

another), show a document at both ends of the

flow line unless the connection is so short that the

intent is unambiguous.



7. Documents or reports printed in a computer facility

should be shown in that facility’s column first. Then

show the document or report going to the

destination unit.

8. Documents or reports printed by a centralized

computer facility on equipment located in

another organizational unit should not be shown

within the computer facility.



9. Processing within an organizational unit on devices

such as a PC, laptop, or computerized cash

register should be shown within the unit or as a

separate column next to that unit, but not in the

central computer facility column.

10. Sequential processing steps (computerized or

manual) with no delay between them (and

resulting from the same input) can be shown as

one process or as a sequence of processes.



11. The only way to get data into or out of a computer

data storage unit is through a computer

processing rectangle or offline process square.

12. Manual process is not needed to show the sending

of a document; sending should be apparent from

the movement of the document.

13. Do not use manual processes to file documents;

show documents going into files.



All documents must have an origin and termination:

each copy of the document must flow to

• a permanent file symbol

• a symbol denoting an exit from the system, or

• an off-page connector

• a document destruction symbol (small black box)

• “cradle to grave” documentation

Make sure progress of a document is clear.

Diagram a document

• before and after each process

• entering or leaving a file

• entering or leaving a page or area of responsibility


Suprina Systems Flowchart


Documenting Enterprise Systems

Moving from a file-based system to an enterprise

database changes the systems flowchart.

• An enterprise database replaces transaction and master

data.

• Other flows may change depending on the system

implementation.


Suprina Systems Flowchart

with an Enterprise Database


Flowchart Summary

• The flowchart is one of the easier types of documentation for information customers and

management to understand.

• Often, auditors use system, document, and procedure

flowcharts to understand business and systems controls

in an environment

• The primary weakness of the flowchart is that it is tied to

physical information flows and system characteristics

that hide the procedural essence of the system.

• Some flowcharts are full of data and processing

artifacts because they are tied to an outdated information technology.



Process Modeling / Documentation

Logical vs. Physical Models

System and Process Concepts

Data Flow Diagrams (DFD)

Elements of a DFD

Rules and Procedures in DFD

23

External Entity

Data Flow

Process

Data Store

DE MARCO & YOURDON

Data Flow Diagrams Symbols

IS 630 : Lecture 3

24

External Entity

Data Flow

Process

Data Store

GANE & SARSON NOTATIONS

Pay Bill

AP Clerk

3

Data Flow Diagrams Symbols

IS 630 : Lecture 3


Why System Modeling

To better understand the system: opportunities for

simplification, optimization (BPR)

To communicate the desired structure and

behavior of the system (business requirements:

data/information & functions/processes)

To visualize and control the system architecture

(blueprint)

To manage risks in development process


Logical Vs. Physical Models

Logical models show WHAT a system is or does. They

are independent of any technical implementation.

Physical models show not only what a system is or does,

but also HOW the system is (to be) physically and

technically implemented. They reflect technology choices.


Why Logical Models

Logical models remove (political, emotional) biases resulted from the way the system is currently implemented, or the way that any one person thinks the system might be implemented.

Logical models reduce the risk of missing business requirements in cases one is too preoccupied with technical results (premature technical solutions).

Logical models allow the communication with end-users in nontechnical or less technical languages (charts, diagrams).


Process Modeling with DFD

Process Modeling is a technique for organizing

and documenting the structure and flow of data

through a system’s processes, and the logic,

policies, and procedures to be implemented by a

system’s processes.

Data Flow Diagram (DFD) is a graphical tool to

depict the flow of data through a system and the

work or processing performed by that system.

Language description (memo) is subject to

interpretation, it may omit crucial info.

DFD is Graphical description the flows of data

within an organization


System Concept

A system exits by taking input from the

environment, transforming (processing) this input,

and release an output

A system may be decomposed (exploded) into

subsystems

A subsystem has its own input and output

Output of one subsystem may become the input

of other subsystems (throughput)

30

Systems & Subsystems

INPUT OUTPUT

IS 630 : Lecture 3


Systems & Processes

A system is a process. It addresses a business function.

A process is work / action performed on, or in response to, incoming data flows or conditions.

A process (function) can be decomposed into sub-processes (sub-functions, tasks)


Decomposition Diagram


Functional Decomposition Diagram


Event Decomposition Diagram


Data Flow Diagrams

DFD documents a business function/activity/task of

a system as a process.

DFD describes how data is manipulated within and

at the boundaries of the system.

DFD shows detail of the interdependency among

processes of the system, movements of data or info

among the processes.


External Entities

An External Entity is a provider (source) or receiver

(sink) of data and info of the system.

An External Entity is NOT part of the system: the

externality depends on how the system is defined.

SUPPLIER


External Entities . . .

An external entity (agent) defines a person,

organization unit, or other organization that lies

outside of the scope of the project but that interacts

with the system being studied.

• External agents define the “boundary” or scope of a system being modeled.

• As scope changes, external agents can become processes,

and vice versa.

• Almost always one of the following:

o Office, department, division inside the business but outside the

system scope.

o An external organization or agency.

o Another business or another information system.

o One of system’s end-users or managers


Data Stores

A Data Store is a storage of data: it contains

information

Physical storage is immaterial : it can be a filing

cabinet, book, computer file

D1 Accounts Receivable


Data Stores . . .

A data store is an inventory of data. • A data store is “data at rest” compared to a data flow

that is “data in motion.”

• Almost always a data store for one of the following:

o Persons (or groups of persons): e.g., customer

o Places: e.g, cash register

o Objects: e.g., product

o Events (about which data is captured): e.g., sales

o Concepts (about which data is important): e.g., discount

• One can identify data stores with REAL (Resources-Events-Agents-Locations) framework

• Data stores depicted on a DFD store all instances of data entities (depicted on an ERD)


Data Flows

A Data Flow represents a movement of data (info) among processes or data stores

A Data Flow does NOT represent a document or a physical good: it represents the exchange of information in the document or about the good

A Data Flow represents an input of data to a process, or the output of data from a process. • A data flow may also be used to represent the creation,

reading, updating, or deletion (CRUD) of data in a file or database (called a data store).

• A composite data flow (packet) is a data flow that consists of other data flows.

DELIVERY SLIP


Processes

A Process is a work or action performed on input

data flow to produce an output data flow

Use a verb to label the action performed by the

process (not the name of person or department

who does it as in physical DFD)

A Process must have at least one input data flow

and at least one output data flow.

1

Pay Bill


Types of Processes

Function: a set of related and ongoing activities of a business: e.g., sales.

Activity (Event / Transaction) : a logical unit of work that must be completed as a whole (as part of a function): e.g., collect payment.

Task (Elementary / Primitive Process): a discrete, detailed activity or task required to respond to an event. Usually, several such tasks must be completed to respond to an activity/ event, e.g, update new info, calculate payment, create notice…


Context Diagram

Define the boundary of the system

Identify the external entities

No detail on processes and data stores of the

system


M

N

P

M

N

P

Context Diagram

Level-0 Diagram

Level-1 Diagram

1 3

2

0

D1


DFD Building Procedure

Context Diagram

• Identify the system and its boundaries (the context)

• Identify external entities (providers, receivers of system info)

• Identify external data flows (input, output)

• Note: the whole system itself is a process (it receives input and

transforms it into output) doing a business function


DFD Building Procedure . . .

Level-0 DFD

• Identify what is being done between each input and its

corresponding output

• Identify the processes (functions of the system)

• Identify external data flows between external entities and

processes

• Identify internal data flows between processes and data stores

Level-1 DFD’s

• Sub-processes (activities or tasks) of Level-0 processes (system

functions)


Rules in DFD Building

Rule 1 : Unique label for each symbol to avoid

confusion

Rule 2 : Use an action VERB to label a process

(because a process is an action !!!)


Rules in DFD Building . . .

Rule 3 : Must be one process associated with each

data flow …

M

M




data flow …

M N

M N




data flow.



Rule 4 : Shaded corner must appear in ALL occurrences

of a duplicated symbol in a same diagram on the same

page.

CUSTOMER

CUSTOMER

D3

D3

Accounts Receivable

Accounts Receivable

1.0

3.0



Rule 5 : No process without output data flow (black hole !!!)



Rule 6 : No process without input data flow (miracle !!!)



Rule 7 : No need for routing (without transforming) a

data flow with a process (non value-added

activities !!!)

Info A Info A



Rule 8 : Identical input, output data flows for parent

and child processes (but the child processes can

have their own throughputs) . Balance Check.


M

N

P

1 2

3

M

N

P

Context Diagram

Level-0 Diagram

Balance Check



Rule 9 : Data flows cannot split by themselves



Rule 9 : Data flows cannot split …



Rule 10 : A data packet can combine many data elements being transmitted at the same time to the same destination (a document carries many pieces of info)



Rule 11 : Double-headed arrows are forbidden [in-

flow (update) and out-flow (extract info) of a data

store carry different information]


Rules in DFD Building ...

Rule 12 : Data flow can NOT go backward in Level-0

(Today’s output can’t go back to yesterday’s work !!!)

Notes: Show

any branching

decision / loop

in Level-1


Differences Between DFDs and Flowcharts

Processes on DFDs can operate in parallel (at-the-same-time) • Processes on flowcharts execute one at a time

DFDs show the flow of data through a system • Flowcharts show the flow of control (sequence and transfer

of control)

Processes on a DFD can have different timing (daily, weekly, on demand) • Processes on flowcharts are part of a single program with

consistent timing


Data Conservation

Data conservation – the practice of ensuring that a

data flow contains only data needed by the

receiving process.

• New emphasis on business process redesign to identify and eliminate inefficiencies.

• Simplifies the interface between those processes.

• Must precisely define the data composition

(attributes/fields) of each data flow (document), expressed

in the form of data structures (in Data Modeling).

• “cradle to grave” documentation

• CRUD Matrix : Create, Read, Update, Delete.


Data to Process Matrix


Architecture Blueprints . . .

F1

F2

F3

Building Plan Level-0 DFD

1.0

2.0

3.0

E1

E2

The building has 3 floors The system has 3 functions

© 2010 D. Nguyen @ CSUN


Floor Plan for F1 Level-1 DFD for 1.0


Floor 1 has a big space for parking

Function 1 has a single task

1.0

No need for Level-1

(can get from Level-0) No need for detail blueprint



2.1

2.3

2.2

Floor Plan for F2 Level-1 DFD for 2.0

2.1

2.2

2.3

(3.0)


Floor 2 has 3 suites

Function 2 has 3 activities

(1.0)



2.1.2 2.1.1

Suite Plan for 2.1 Level-2 DFD for 2.1

2.1.1

2.1.2

(2.2)


Suite 2.1 has 2 rooms Activity 2.1 has 2 tasks


(1.0)

Linked Processes

1.0

2.0

1.0

2.0

D1

1.0 sends data to 2.0 1.0 and 2.0 share the

same data store D1



1.1

1.2

1.3

2.1

2.2

2.3

(EXTRA STEP) (CONDITIONAL EXIT)

IF (Condition)

DO “1.2”

IF (Condition)

DO “2.2”

ELSE

DO “2.3”

(2.0) (3.0)

Note: Show conditional branching in Level-1 DFD’s or lower.

Conditional Branching


DFD Deliverables

Current System • Context Diagram

• Logical Level-0 DFD

• Logical Level-1 DFD’s (multi-task functions)

• Physical Level-0 DFD [for AUDITING]

• Physical Level-1 DFD’s (multi-task functions)[for AUDITING]

Proposed System • Context Diagram

• Logical Level-0 DFD

• Logical Level-1 DFD’s (multi-task functions)

• Physical Level-0 DFD [for implementation]

• Physical Level-1 DFD’s (multi-task functions)[for implementation]