Systems Analysis and Design

CIS 2303

Learning Outcome 3:

Produce logical models that graphically describe a system using different modeling techniques.

- Functional Decomposition Diagrams – Ch. 4

- Use Case Diagrams – Ch. 6

- Data Flow Diagrams – Ch. 5

Learning Objectives1. Introduction to Process Modeling

Describe the difference between Logical and Physical Models

Describe Modeling Tools and Techniques

2. Functional Decomposition Diagrams

Use a Functional Decomposition Diagram (FDD) to model Business Functions and Models

3. Use Case Diagrams

Describe the symbols used in Use Case diagrams and explain the rules for their use

2

Learning Objectives –cont.4. Data Flow Diagrams: Describe the symbols used in Data Flow diagrams

and explain the rules for their use

Draw Context Diagrams

Draw Data Flow diagrams in a sequence, from general to specific

Explain how to level and balance a set of data flow diagrams

3

1. Introduction to Process Modeling

 

A. Modeling Tools and Techniques

B. Differentiate between Logical and Physical Models

4

B. Modeling Tools and Techniques

Functional Decomposition Diagrams

Use Case DiagramsData Flow Diagrams

◦Context Diagram◦Diagram 0 DFD◦Lower Level Diagrams

5

C. Logical Versus Physical Models

Logical model shows what the system must do

Physical model describes how the system will be constructed

A physical model shows how the system’s requirements are implemented

6

2. Functional Decomposition Diagrams

7

Functional decomposition diagram (FDD) is◦A top down representation of a business process

◦Drawn like an organization Chart◦Business functions or processes are broken down to lower level processes or functions

During application development, these processes become program modules

Sample FDD

8

Patient Appointment Management

Registration

New Patient Registration

Update Registrati

on

Treatment

Update Treatment Records

Billing

Update Billing History

Generate Reports

9

Exericse-1Draw a FDD for the Portal System in your

college. Your FDD must consist of 3 levels. Write your assumptions if any.

3. Use Case Diagrams

10

Use Case Modeling◦ Unified Modeling

Language◦ Actor

◦Symbol for a Use Case is an oval with a label that describes the action or event

◦Use cases also can interact with other use cases

3. Use Case Diagrams –cont.

11

Use Case Diagrams◦Use case diagram ◦System boundary◦After you identify

the system boundary, you place the use cases on the diagram, add the actors, and show the relationships Figure 6-27

4. Data Flow Diagrams

A. What is a Data Flow Diagram? 

B. Describe the Different Versions of DFD Symbol Sets

C. Describe the Process Symbol

D. Describe the Data Flow Symbol

E. Describe the Data Store Symbol

F. Describe the Entity Symbol

12

4. Data Flow Diagrams –cont.

G. Drawing DFDs: Step 1 – Context Diagram

H. Drawing DFDs: Step 2 – Diagram 0

I. Drawing DFDs: Step 3 – Leveling and Balancing DFDs

J. Guidelines for Drawing DFDs

13

A. Overview of a Data Flow Diagram (DFD)

A data flow diagram (DFD) shows how data moves through an information system but does not show program logic or processing steps

A set of DFDs provides a logical model that shows what the system does, not how it does it

14

B. DFD Symbol Sets

Figure 5-3

15

C. DFD Symbols: The Process Symbol

Receives input data and produces output that has a different content, form, or both

Contain the business logic, also called business rules

Referred to as a black box

16

D. DFD Symbols: The Data Flow Symbol

Represents one or more data items

The symbol for a data flow is a line with a single or double arrowhead

Spontaneous generation

Black holeGray hole

17

18

Exercise-2

Study the Three INCORRECT Data Flow and Process Combinations found on Page 203 of your textbook

Draw one example for each of the following processes:Spontaneous GenerationBlack HoleGray Hole

E. DFD Symbols: The Data Store Symbol

Represent data that the system stores

The physical characteristics of a data store are unimportant because you are concerned only with a logical model

19

20

Exercise-3Study the INCORRECT uses of Data Store Symbols on Page 204 of your textbook 1. Draw an example for each incorrect use of

a data store2. Draw a corrected version for each of the

incorrect uses that you did in step 1

Name of the entity appears inside the symbol

TerminatorsSourceSink

21

F. DFD Symbols: The Entity Symbol

22

Exercise-4What is the difference between a source

entity and a sink entity? Draw an example for each one

Study the INCORRECT uses of Entity Symbols on Page 205 of your textbook.

1. Draw an example for each incorrect use of an entity

2. Draw a corrected version for each of the incorrect uses that you did in step 1

23

Exercise-5provide some examples for a Process Name in a Company

provide some examples for an Entity Name in a Company

Give an example of a Process that receives two inputs and produces one output

G. Creating a Set of DFDs: Context Diagram

Step 1: Draw a Context Diagram

24

25

Exericse-5Explain in your own words the Context Diagram for the Order System shown in Figure 5-13 on Page 208 of your textbook, taking into consideration the Following:What is the Process in the Diagram and what

does it represent?What are the External Entities in the

System? Which entities are Sources and which are Sinks?

Explain what happens between the Order System and Each of the Entities

H. Creating a Set of DFDs: Diagram 0 DFD

Step 2: Draw a Diagram 0 DFD

26

Step 2: Draw a Diagram 0 DFD◦If same data flows in both directions,

you can use a double-headed arrow◦Diagram 0 is an exploded view of

process 0◦Parent diagram◦Child diagram◦Functional primitive

27

H. Creating a Set of DFDs: Diagram 0 DFD –Cont.

28

Exericse-6Study Diagram 0 for the Grading System shown in Figure 5-15 on Page 210 of your textbook, taking into consideration the following:What are the Main Processes that the

Grading System consists of?Explain what happens between each entity

and the processes that this entity interacts with

Explain the importance of the data store(s) found in the Diagram.

I. Creating a Set of DFDs: Leveling DFDs

Step 3: Draw the Lower-Level Diagrams◦ Must use leveling

and balancing techniques

◦ Leveling examples Uses a series of

increasingly detailed DFDs to describe an information system

Exploding, partitioning, or decomposing 29

Step 3: Draw the Lower-Level Diagrams◦ Balancing

Examples Ensures that the

input and output data flows of the parent DFD are maintained on the child DFD

30

I. Creating a Set of DFDs: Balancing DFDs

J. Guidelines for Drawing DFDs

Draw the context diagram so that it fits on one page

Use the name of the information system as the process name in the context diagram

Use unique names within each set of symbols

31

Do not cross linesProvide a unique name and

reference number for each process

Obtain as much user input and feedback as possible

32

J. Guidelines for Drawing DFDs –Cont.

Review Questions

What is the main difference between logical and physical models?

What are the names of the different process modeling tools and techniques.

What is a functional decomposition diagram? Why is it used? How can this diagram be used during applications development?

Describe the main notations used in a Use Case Diagram.

Describe the Gane and Sarson symbols used in Data Flow Diagrams.

Give four examples of processes, data flows, data stores, and entities relating to any business process

33

Review Questions –Cont.

What is the relationship between a context diagram and diagram 0, and which symbol(s) is not used in a context diagram?

What is meant by an exploded DFD?Explain the DFD leveling technique.What is a balanced DFD?

34