Ch 5 Lesson 1

1
Systems analysis and design

• Chapter 5 Lesson 1 DFD Fundamentals 

2
Using Data Flow Diagram
DLSU-Dasmariñas-Cavite
Systems Analysis and Design

• A graphical tool that depicts the flow of data in
  an information systems the relationships among
  the data flows and how data come to be stored at
  specific location.
• Represents the functions or processes which
  capture manipulate store and distribute data
  between a system and its environment and between
  components within a system.
• Is a process modeling tool that depicts the flow
  of data through a system and the work or
  processing performed by that system
• emphasize the logic underlying the system
• The systems analysts can put together a graphical
  representation of data movement through the
  organization

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Using Data Flow Diagram
3
Using Data Flow Diagram
DLSU-Dasmariñas-Cavite
Systems Analysis and Design

• Advantages of the Data Flow Diagram Approach
• Freedom from committing to the technical
  implementation too early
• Understanding of the interrelationships of
  systems and subsystems
• Communicating current system knowledge to users
• Analysis of the proposed system

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Using Data Flow Diagram
4
Basic Symbols
5
Basic Symbols

• Four basic symbols are
• A double square for an external entity--a source
  or destination of data.
• An arrow for movement of data from one point to
  another.
• A rectangle with rounded corners for the
  occurrence of transforming process.
• An open-ended rectangle for a data store.

6
Types Data Flow Diagram
Systems Analysis and Design
DLSU-Dasmariñas-Cavite

• Context Diagram
• A data flow diagram (DFD) that shows the system
  boundaries external entities that interact with
  the system and the major information flows
  between the entities and the system
• Level-O Diagram
• A data flow diagram (DFD) that represents a
  systems major processes data flows and data
  stores at a high level of detail

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Using Data Flow Diagram
7
Context Diagram
DLSU-Dasmariñas-Cavite
Systems Analysis and Design

• Each context diagram must fit on one page.
• The process name in the context diagram should be
  the name of the information system.
• Use unique names within each set of symbols.
• Do not cross lines. Restrict the number of
  symbols and in lower level diagrams you should
  not have more than nine process symbols.
• Use a unique reference number for each process
  symbol.

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Using Data Flow Diagram
8
External Entities

• Represent people or organizations outside of the
  system being studied
• Shows the initial source and final recipient of
  data and information
• Should be named with a noun describing that
  entity

9
External Entities (Continued)

• External entities may be
• A person such as CUSTOMER or STUDENT.
• A company or organization such as BANK or
  SUPPLIER.
• Another department within the company such as
  ORDER FULFILLMENT.
• Another system or subsystem such as the
  INVENTORY CONTROL SYSTEM.

10
External Entities
DLSU-Dasmariñas-Cavite
Systems Analysis and Design

• External Entities
• Represent people or organizations outside of the
  system being studied
• Shows the initial source and final recipient of
  data and information
• Should be named with a noun describing that
  entity
• External entities may be
• A person such as CUSTOMER or STUDENT
• A company or organization such as BANK or
  SUPPLIER
• Another department within the company such as
  ORDER FULFILLMENT
• Another system or subsystem such as the
  INVENTORY CONTROL SYSTEM

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Using Data Flow Diagram
11
Processes

• Represent either
• A whole system
• A subsystem
• Work being done an activity
• Names should be in the form verb-adjective-noun
• The exception is a process that represents an
  entire system or subsystem.

12
Data Stores

• Name with a noun describing the data
• Data stores are usually given a unique reference
  number such as D1 D2 D3.
• Include any data stored such as
• A computer file or database.
• A transaction file .
• A set of tables .
• A manual file of records.