Process models data flow diagrams
Download
1 / 31

Process Models: Data Flow Diagrams - PowerPoint PPT Presentation


  • 235 Views
  • Uploaded on

Process Models: Data Flow Diagrams. Special thanks goes to Dr. Jack T. Marchewka for many of the ideas and examples contained in these notes. Process Modeling. Objective: Understand the concept of business processes Understand and create Data Flow Diagrams. DFDs. Visually represent

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Process Models: Data Flow Diagrams' - dorjan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Process models data flow diagrams

Process Models:Data Flow Diagrams

Special thanks goes to Dr. Jack T. Marchewka for many of the ideas and examples contained in these notes.


Process modeling
Process Modeling

  • Objective:

    • Understand the concept of business processes

    • Understand and create Data Flow Diagrams.


DFDs

  • Visually represent

    • data flows

    • processes

  • Emphasize the logic of system

  • Provide documentation for Analysis & Design


Data Flow Diagrams

Data Flow

Process

File or Data Store

Source or Entity

Gane & Sarson Methodology


DFDs

  • Do not show technical aspects

  • Show interrelations of systems & subsystems

  • Facilitates

    • developer understanding

    • user-developer communication

  • Completeness of data & process definitions


The systems concept
The Systems Concept

Output

Input

Process


DFDs

1

Data Flow

Input

Data Flow

Output

Process


Developing dfds
Developing DFDs

  • Context Diagram

    • System Overview

    • Little or no detail

  • Zero Level Explosion

    • More detailed

  • First,Second, Third Levels

    • More detailed levels


Context dfd
Context DFD

  • Basic overview of the system

  • Contains only 1 process

    • given the number zero

  • Shows all external entities

  • Major data flows among entities

  • Generally no data stores

  • Assign a name to the whole system


Context dfd examples
Context DFD Examples

Apartment Rental

Receipts, Notices

Lease

Cash

Report

0

External

Manager

Apartment

Rental

System

Tenant

Lease,

Payments

Bank Deposit

Bank


Recall on line university registration from use case examples
Recall: on-line university registration (from Use Case examples)

The system should enable the staff of each academic department to examine the course offered by their department, add and remove course, and change the information about them (e.g., the maximum number of students). It should permit students to examine currently available courses, add and drop courses to and from their schedules, and examine the course for which they are enrolled. Department staff should be able to print a variety of reports about the courses and the students enrolled in them. They system should ensure that no student takes too many course and that students who have any unpaid fees are not permitted to register. (Assume that a fees data store is maintained by the university's financial office that the registration system accesses but does not change.)


Course examples)

Registration

System

Registration Context Diagram

0

Course

information

Enrollment

information

Department

Staff

Students

Course

offerings

Student

schedules


Recall real estate from use case examples
Recall: real estate (from Use Case examples) examples)

A Real Estate Inc. (AREI) sells houses. People who want to sell their houses sign a contract with AREI and provide information on their house. This information is kept in a database by AREI and a subset of this information is sent to the citywide multiple-listing service used by all real estate agents. AREI works with two types of potential buyers. Some buyers have an interest in one specific house. In this case, AREI prints information from its database, which the real estate agent uses to help show the house to the buyer (a process beyond the scope of the system to be modeled). Other buyers seek AREI’s advice in finding a house that meets their needs. In this case, the buyer completes a buyer information form that is entered into a buyer database, and AREI real estate agents use its information to search AREI’s database and the multiple-listing service for houses that meet their needs. The results of these searches are printed and used to help the real estate agent show houses to the buyer.


AREI examples)

System

AREI Context Diagram

0

Buyer

information

Sellers

Buyers

House

information

House

information

House

Information

House

Information

Multiple

Listing

Service


Level 0 dfd
Level 0 DFD examples)

  • Detail from “exploding” the context-level DFD

  • Show less than 9 processes

  • Number each process

  • Show data stores (master files)

  • Ignore the handling of exceptions

  • Show all external entities


Level 0 DFD: Apartment Rental examples)

Tenant Info

D1

Tenant File

Copy of lease

1

Lease

New

Tenant

Process

Receipt

Bank

Deposit

Tenant

Bank

2

Payments

Collection

Process

Notice

Cash Report

Unpaid

Charges

Tenant

Info

Ext.

Mgr

3

D1

Tenant File

Delinquent

Process

Delinquency

Report

Delinquencies


1 examples)

Maintain

department

course

offerings

D3

D2

D1

Fees

2

Course Offerings

Maintain

student

enrollments

Enrollments

3

Course

Enrollment

Reports

Level 0 DFD: Registration

Course Offering

Changes

Available

course request

Available

courses

Available

courses

Course Offering

List

Students

Available courses

Course enrollment

Course

Offering

Updates

Course

Offerings

Student schedule

Course

enrollment

request

Dept

Staff

Student

schedule

Course

information

Fee Payment

History

Student Enrollment

Report Request

Enrollment

information

Student

Enrollment

Report


Maintain examples)

house

seller

information

D4

D2

D3

D1

Sales

Contract

1

Sales Contract

Sellers

Multiple Listing

Services File

House information

House information

House information

House information

Offered Houses

Buyers

Sales Contracts

House

information

Generate

requested

report

2

House information request

Buyers

Buyer information form

Buyer

information

House information

Level 0 DFD: AREI


Create child diagrams
Create Child Diagrams examples)

  • Vertical Balancing

    • A child diagram cannot produce output or receive input that the parent does not produce or receive

  • External entities are not shown

  • May contain additional data stores

    • e.g.., transaction files

  • Primitive when no longer exploded


Level 1 DFD: Apartment Rental examples)

2.1

Deposit Checks

Deposit Receipts

Collect

Security

Deposit

Tenant

Info

Bank Deposit

D1

Tenant File

Tenant

Info

Bank Deposit

2.2

Rent Checks

Payment Receipts

Collect

Rent

Cash

Report

Unpaid

Charges


Level 2 DFD: Apartment Rental examples)

2.1.1

Deposit

Check

Bank Deposit

Make

Bank

Deposit

Deposit

Info

2.1.2

Update

Info

Update

Tenant

File

D1

Tenant File

2.1.3

Receipt

Tenant

Info

Create

Receipt


Produce examples)

course

offering

list

D2

Department ID

1.1

Course offering list

Course Offering

List Request

Department ID

1.2

New Course

New Course

information

Dept.

Staff

Course Offerings

1.3

Course to

delete

Delete

course

Add new

course

Course to delete

Existing Course

information

1.4

Course modifications

Course modifications

Modify

existing

courses

Level 1 DFD (1 of 3): Registration


Produce examples)

course

offering

list

D1

D3

D2

Fees

Enrollments

Course Offerings

Delete

course from

schedule

Add course

to schedule

Obtain

current

schedule

Level 1 DFD (2 of 3): Registration

Available Course

Request

2.1

Available courses

Available

Courses

2.2

Course enrollment add

Course to add

to enrollment

Fee payment history

Students

Course enrollment

add

2.3

Course to

delete

Course to delete

2.4

Student enrollment

information

Current schedule request

Student schedule


Obtain examples)

report

type

D3

D2

3.1

Report

Request

Report

type

Course offering

information

Dept.

Staff

Enrollments

Course Offerings

3.2

Generate

requested

report

Enrollment

information

Requested

report

Level 1 DFD (3 of 3): Registration


Common errors
Common Errors examples)

  • Forgetting data flows

  • Arrow pointing wrong way

  • Connecting data stores & sources

  • Incorrectly labeling processes or flows

  • Too many processes (break it up!)

  • Data flows entering a process must be different when leaving!


Logical physical dfds
Logical & Physical DFDs examples)

  • Logical

    • focuses on modeling the business

    • system independent

  • Physical

    • focuses on modeling the system

    • system dependent


Logical dfds current system
Logical DFDs - Current System examples)

  • Good for communication & understanding

  • Focus on business activities

    • User view of the current system

  • Model of the business


Logical dfds new system
Logical DFDs - New System examples)

  • Look for improvements

    • effectiveness - i.e., doing the “right thing”

    • efficiency - i.e., doing the “thing right”

  • Transition from “Analysis” to “Design”


Physical dfds
Physical DFDs examples)

  • Use the new logical DFD to make transition to a CBIS

  • Define Machine versus manual boundaries

    • processes = programs or manual procedures

    • data stores = data files or manual files

  • Define controls, validations, & security

  • Define actual file names & printouts

    • Master & transaction files


Partitioning the physical dfd
Partitioning the Physical DFD examples)

  • Defining

    • manual procedures

    • automated procedures

      • circled using a dotted line

  • Batch versus On-Line Procedures


2.1.1 examples)

Deposit

Check

Bank Deposit

Make

Bank

Deposit

Deposit

Info

2.1.2

Update

Info

Update

Tenant

File

D1

Tenant File

2.1.3

Receipt

Tenant

Info

Create

Receipt


ad