PHASE 2 :
SYSTEM ANALYSIS
LESSON 5
PROCESS MODELING
INTRODUCTION
In the previous lesson, we have learned data modeling. Data modeling is a technique for
defining business requirements for database. After we have completed the data modeling with
an ER-Diagram, we can continue with the process modeling. In this lesson, we will continue the
discussion on process modeling. We will discuss how the requirements definition and use cases
are further defined into a process model. In this lesson, our focus on one tool that is used to
represent the information gathered as parts of requirements gathering – data flow diagram. This
lesson consists of four sections :

Overview of process modeling

DFD symbols

Drawing DFD

Use Case
LEARNING OUTCOMES
At the end of this lesson, students should be able to :

define process modeling

differentiate DFD symbols

draw DFD

use a case as a process modeling
TERMINOLOGY
No
1
Word
Context diagram
Definition
A diagram that shows the system boundaries, external agents
that interact with the system and major flows between them
2
Data flow
A data that is input or output to or from a process
3
Data flow diagram
A process model used to depict the flow of data through a
system and work done by the system
4
Data store
A stored data intended for later use
5
External agents
An outside person, organization unit, system or other
organization that interact with the system
6
Process
A work performed by a system in response to incoming data
flows or conditions
7
Process modeling
A process-centered technique used to organize and document
a system’s processes
5.1
OVERVIEW OF PROCESS MODELING
System
Planning
Requirements Gathering
Data Modeling
√ Process Modeling
System
Analysis
System
Design
System
Implementation
System
Maintenance
Figure 5-1: Process Modeling Activities in the System Analysis Phase
Process modeling is a formal way of representing how an information system operates. It
illustrates the processes or activities that are performed and how data moves among them in
the system environment. Process modeling involves representing the functions, processes,
manipulate, store and distribute the data among them and its environment. There are many
different process modeling techniques can be used today. The most popular one is Data flow
diagram (DFD). Data flow diagramming is a technique that diagrams the processes and the data
passes among them in the system. It’s a traditional process modeling technique of structured
analysis and design. Data flow diagram uses various symbols to show how the system
transforms input data into useful information. There are two standard sets of data flow diagram
symbols being used; DeMarco and Yourdon and Gane and Sarson.
5.2
DFD SYMBOLS
Before we start draw a DFD for the system, we need to understand various types of symbols in
DFD. DFD uses four basic symbols that represent processes, data flows, data stores and
entities. Both standards; DeMarco and Yourdon and Gane and Sarson have a different ways to
represent the symbols. Figure 5-2 shows how both standards represent the symbols for DFD.
Symbol Name
External Agents
Data Store
Process
Gane & Sarson Symbols
Yourdon Symbols
Name
Name
Name
Name
Name
Name
Data Flow
Figure 5-2: DFD Symbols
5.2.1
External Agents
All information systems respond to events and conditions in the system’s environment. System’s
environment includes external agents that form the boundary of the system and define where
the system interfaces with its environment. It’s also referring to source or sink. External agents
give an input to a system and receive an output from the system.
An external agent of an information system are already fixed and defined. When the system is
getting big, the external agents may be changed. An external agent can be an outside person,
organization unit, system or organization that interacts with a system and eternal organization It
can be such as :

An office, department, division or individual from the same organization

An organization, agency, or individual that is outside the organization

Another business or information system

System’s end users or managers
Figure 5-2 shows how to represent an external agent. The name of the entity appears inside the
symbols. External agents should be named with descriptive, singular nouns such as VENDOR
and ACCOUNTING SYSTEM. System analyst called an external agent that supplies data to the
system a source, and an entity that receives data from a system a sink. An external entity can
be a source or a sink or both, but each entity must be connected to a process by a data flow.
5.2.2
Data Store
Information system captures data to be used. This data is kept in a data store. A data store is
used in a DFD in order to represent data that the system stores because one or more processes
need to use the data. For instance, lecturers need to store student’s scores on tests and
assignments during the semester so that they can assign final grades at the end of the
semester.
Figure 5-2 shows how to represent the data store. The name of the data store appears between
the lines and identifies the data contains. A data store name should be in plural name consisting
of a noun and adjectives, if needed. An example of data store is STUDENTS, ACCOUNT
HOLDERS, INSURANCE POLICIES, and others. A data stores must be connected to a process
with a data flow. Data stores describe things about which the business wants to store data such
as :

Persons : STUDENT, LECTURER, ADMINISTRATOR, DEPARTMENT

Places : BUILDING, BLOCK, ROOM, BRANCH OFFICE

Objects : BOOK, VEHICLE, PRODUCT

Events : APPLICATION, LECTURE, REGISTRATION, RENEWAL

Concepts : ACCOUNT, COURSE, QUALIFICATION, FUND
5.2.3
Process
A system is a combination of processes. A process receives input data and produces output
that has a different content, form or both and have a meaning for its environment. The process
defines the boundary of the system. The system is must be inside the boundary. The system
exchanges the input and output within its environment through a process. A process is a work
performed by a system in response to incoming data flows or conditions. Figure 5-2 shows how
to represent a process. The name of the process appears inside the rectangle the process
name should identifies a specific function and consists of verbs (and adjective, if necessary)
followed by a singular nouns. For example of process name are APPLY RENT PAYMENT,
CALCULATE COMMISION, ASSIGN MARK and VERIFY ORDERS.
5.2.4
Data Flow
As stated earlier, process respond to inputs and generate outputs. Meaning that each process
should have at least one input and one output data flow. A data flow is a path for data to move
from one part of the information system to another. A data flow in information system represents
one or more data items. For example, a data flow could consist of a single data item (such as
STUDENT_ID) or a set of data (such as class roster with student ID number, names, address).
A data flow represents an input of data to a process or the output of data from a process. A data
flow also represent the creation, reading, deletion or updating of data in a file or a database.
Database is refers as data store in a DFD. Figure 5-2 shows how to represent a data flow
symbols. The data flow name appears above, below or alongside with the line.
5.2.5
Exercises
Answer TRUE or for FALSE for each of the questions below.
1. A data flow diagram is a process model. TRUE
2. A system is a combination of processes. TRUE
3. In a data flow diagram, rounded rectangles are used to represent a process. FALSE
4. The calculation of a student’s grade is represented on a data flow diagram as a process.
TRUE
5. Sources and sinks are internal to the system. FALSE
5.3
DRAWING DFD
5.3.1
Context diagram
Student info
Lecturer Info
STUDENT
LECTURER
Registration slip
Fee Status
COURSE
Course Assigned
COURSE
REGISRTATION
SYSTEM
Course Info
Student info
Fee Status
STUDENT
FINANCIAL
SYSTEM
Figure 5-3: Context Diagram for Course Registration System
5.3.2
Diagram 0 DFD
STUDENT
Student info
Course info
1
Register
Student info
Course
2
Registration Report
Produce
Registration
report
List Course
Offered
STUDENT
COURSE
3
Lecturer Info
Courses
Course
Fee status
Student info
LECTURER
Assigned
4
Fee status
Check Fee
status
Student info
Course
Assigned
STUDENT
FINANCIAL
SYSTEM
Figure 5-4: An example of Diagram 0 DFD for Course Registration System
5.3.3
Lower-level Diagram
1.1
Matric Num
Get student
profile
Fee status
1.2
Student Info
Register
course
List courses
1.3
View
course
Course Info
COURSE
Figure 5-5: An example of one of the lower level diagram for Course Registration System
5.3.4
Exercises
Answer TRUE or for FALSE for each of the questions below.
1. Context diagrams have only more than one process. TRUE
2. A context data flow diagram defines the scope and boundary for the system and project.
TRUE
3. A data flow cannot go directly back to the same process it leaves. TRUE
4. Data cannot move directly from a source to a sink. FALSE
5. The lowest-level data flow diagrams are called level-0 diagrams. FALSE
5.4
USE CASE
Data flow diagram is a popular modeling tool that you can use to show system’s functionality
and the flow of data. Use case modeling is another way to show the system’s functionality. Use
case modeling helps the analyst to analyze the functional requirements of a system. Although
use case modeling is often associated with object oriented system analysis and design, but the
concepts is flexible enough, so it can be used in traditional approach of system analysis and
design.
5.4.1
Use Case
Use case modeling identifies and describes the system functions by using a tool called use
cases. A use case is a depiction of a system’s behavior or functionality under various conditions
as the system responds to requests from users (Hoffer et. al., 2005). A use case represents a
single goal of the system and describes a sequence of activities and user interactions in trying
to accomplish the goal. It describes the behavior of the system under the various situations as
the system responds to request from principal actors. An actor initiates the request to the
system, and the system responds the request. Use cases are represented by a horizontal
ellipse with the name of the use case appearing above, below or inside the ellipse. A use case
can be stated in a present-tenses verb phrase, containing the verbs (what should the system
do) and the objects of the system (what the system should act on).
5.4.2
Actors
A use case diagram consists of use cases and actors. An actor is anything that needs to interact
with the system to exchange information. An actor initiates system activities; known as use case
for the purpose of completing some task defined. A user is anyone who uses the system. An
actor represents a role fulfilled by a user interacting with the system. An actor is not only human
being but also can be organization, other information system. Figure 5-6 shows an example of
representation of actor. There are four types of actors :

primary business actor – the stakeholder which primarily benefits from the execution of
the use case by receiving something of measurable

primary system actor – the stakeholder that directly interfaces with the system to initiate
the business or system events

external server actor – the stakeholder that responds to a request from the use case
defined

external receiver actor – the stakeholder that is not primary actor but receives something
of measurable from the use case.
Figure 5-6: An Actor
5.4.3
Relationship
A relationship is depicted as a line between two symbols on the use-case diagram. There are
several meanings of the relationship, depends on how the lines are drawn and what types of
symbols are connected. This type of relationship is:

Association – a relationship between an actor and a use case exists when ever the use
case describes an interaction between them. Association contains an arrowhead at the
end touching the use case indicate that the use case was imitated by the actor on the
other end of line. An association without an arrowhead indicates an interaction between
the use case and external server or receiver actor.

Extend Relationship – a use case may contain complex functionality consisting several
steps which make it difficult to understand. So, to make it simpler, we can extend the
relationship. It extends the use case by adding new behaviors or actions. It’s shown as a
dotted line arrow pointing towards the use case that have been extended and labeled
with the <<extend>> symbol.

Include Relationship – a use case may contain several steps of functionality where we
can combine this step to reduce redundancy. It’s an association between two use cases
where one use case uses the functionality contained in the other. An include relationship
implies that the use case where the arrow originates uses the use case where the arrow
ends while it’s executing. It’s shown as a dotted line arrow pointing towards the use case
that is being used and labeled with the <<include>> symbol.
5.4.4
Exercises
Answer TRUE or for FALSE for each of the questions below.
1.
A use case is a depiction of a system’s behavior or functionality under various conditions as
the system responds to requests from users. TRUE
2.
Use case analysis is the process of identifying and modeling business events, who initiated
them, and how the system responds. TRUE
3.
A relationship is anything that needs to interact with the system to exchange information.
FALSE
4.
An actor is not only human being but also can be organization, other information system.
TRUE
5.
Include relationship is a relationship type between an actor and a use case exists whenever
the use case describe an interaction between them. FALSE
SUMMARY
This is the end of lesson Five. In this lesson, we have learned :

Overview of process modeling

DFD symbols

Drawing DFD

Use Case
In the next lesson, we will continue our discussion on how to conduct an assessment before the
information system project will be develop.
SELF ASSESSMENT
Fill in with the correct answer
1.
_________________________ is a technique for organizing and documenting the structure
and flow of data through a system's processes and /or the logic, policies and procedures to
be implemented by a system's processes. Process modeling
2.
A(n)_________________________ is a graphical tool that allows analysts to illustrate the
flow of data in an information system. data flow diagram
3.
A (n)_________________________ is used in a DFD in order to represent data that the
system stores because one or more processes need to use the data. data store
4.
A process receives _________________________ data and produces _________________________ that has meaning to its environment. Input; output
5.
A _________________________ shows the scope of the organizational system, system
boundaries, external entities that interact with the system, and major information flows
between entities and the system. context diagram
6.
_________________________ is an iterative process of breaking the description of a
system down into finer and finer detail. Functional decomposition
7.
A _________________________ is a data flow diagram that represents a system’s major
processes, data flows, and data stores at a high level of detail. level-0 diagram
8.
A _________________________ is a depiction of a system’s behavior or functionality
under various conditions as the system responds to requests from users. use case
9.
An _________________________ is anything that needs to interact with the system to
exchange information. Actor
10. _________________________ is a relationship between an actor and a use case exists
when ever the use case describes an interaction between them. Association relationship