Chapter 7 : Logical Modelling

Question 1

What is the purpose of Data Flow Diagrams?

Answer 1

1. To show the process that data undergo in a system
2. To show how data moves and changes through an information system in a graphical
3. To produce a logical model of an information system in a simple, direct way

Question 2

List out 4 Components of DFD

Answer 2

1. External Entities / Source & Sink
2. Process
3. Data Flow
4. Data Store

Question 3

List out 2 type of symbols representing DFD?

Answer 3

1. Gane and Sarson Symbols
2. Yourdon Symbols

• View symbols at slide 8

Question 4

What does External Entities / Source & Sink also known as?

Answer 4

1. Terminators

Question 5

What is External Entities / Source & Sink / Terminators?

Answer 5

1. Is a person, dept, outside organization or other information system that provides data to the system or receives data from the system

• May be a source, sink or both

Question 6

What is Source also known as?

Answer 6

1. Origin

Question 7

What is a Source

Answer 7

1. An external entity that supplies data

Question 8

What is a Sink?

Answer 8

1. An external entity that receives data

Question 9

What is Sink also known as ?

Answer 9

1. Sink

Question 10

What is process also known as? ( 2 )

Answer 10

1. Bubble
2. Transform

Question 11

What does Process modifies?

Answer 11

1. Modifies or change data from one form to another form

• Is named to identify the function it accomplishes

Question 12

What is the rule for process in a diagram?

Answer 12

1. A diagram should have no more than 9 process symbols

Question 13

What does Data Flow represents?

Answer 13

1. Represents the transfer of data among data stores, sources or sinks, and processes

• Line can be curved or straight

Question 14

What is Data Store?

Answer 14

1. A data repository

Question 15

When is Data Store used?

Answer 15

1.It is used when the system must store data because one or more processes need to use the stored data a later time

Question 16

What is the rule for Data Store?

Answer 16

1. Process may connect to data storesd

Question 17

What is a Data Flow Diagram ?

Answer 17

1. Is a scope of an organizational system that shows the system boundaries, external entities that interact with the system and the major information flows between the entities and the syste

Question 18

What is a Context Diagram ( DFD ) ?

Answer 18

1. Top-level view of the information system

Question 19

What are the symbols used in Context Diagram?

Answer 19

1. One process symbol representing the entire information system
2. Has the external entities around the perimeter of the page
3. Use data flow to connect the external entities with the process

Question 20

List out things that I need to identify when drawing context diagram ( 3 )

Answer 20

1. Identify Process ( Name of the system )
2. Identify External Entities ( Stakeholder )
3. Identify Data Flows

Question 21

List out 6 guidelines for drawing DFD

Answer 21

1. Draw the context diagram so that it fits on one page
2. Use the name of the information system as the process name in the context diagram
3. Use unique names within each set of symbols
4. Do no cross lines
5. Provide a unique name and reference number for each process
6. Ensure that the model is accurate, easy to understand, and meets the needs of its users

Question 22

List out rules between source to sink in Basic Data Flow Diagram

Answer 22

1. A source or a sink cannot provide data to another source or sink without some processing occurring

• Entity ( Source ) -> Process -> Entity ( Sink )

Source must pass through Process before entering Sink

Question 23

List out rules between source ( Entity ) to data store in Basic Data Flow Diagram

Answer 23

1. Data cannot move directly from a source to a data store without being processed

• Entity ( Source ) -> Process -> Entity ( Sink )

Source must pass through Process before entering Data Store

Question 24

List out rules between Data Store to Sink ( Entity ) in Basic Data Flow Diagram?

Answer 24

1. Data connot move directly from a Data Store to Sink ( Entity ) without being processed

• Data Store -> Process -> Entity ( Sink )

Data Store must pass through Process before entering Sink ( Entity )

Question 25

List out rules between Data Store to Data Store in Basic Data Flow Diagram?

Answer 25

1. Data cannot move directly from one data store to another without being processed * Data Store -> Process -> Data Store **Data Store** must pass through **Process** before entering **Data Store**

Question 26

What is lower level diagrams also called?

Answer 26

1. Child Diagram

Question 27

What is Child Diagram exploded from?

Answer 27

1. Parent Diagram

Question 28

What is the rules for drawing Low-level Diagrams? ( 2 )

Answer 28

1. Leveled - Also called exploded, partitioned and decomposed - Drawn in a series of increasingly detailed diagrams until desired degree of detailed is reached 2. Balanced - Maintain consistency among the entire series of diagrams

Question 29

How many level do we need to create for DFD?

Answer 29

1. Depend on how many **Process** needed Order System Level 0 1. Fill Order 2. Create Invoice 3. Apply Payment * 3 Process 3 Level Level 1 - Make more detail on Fill Order Level 2 - Make more detail on Create Invoice Level 3 - Make more detail on Apply Payment

Question 30

What are the rules for creating Level 0 DFD

Answer 30

1. If same data flows in both directions, I can use a double-headed arrow 2. Diagram 0 is an exploded view of Process 0 3. Parent Diagram 4. Child Diagram * Process 0 Order Management System Level 0 DFD 1. Fill Order 2. Create Invoice 3. Apply Payment

Question 31

What is the next step after creating Level 0 DFD?

Answer 31

1. Draw the Lower Level Diagrams * The level are depend on Process

Question 32

What is the techniques that Leveling must use? ( 2 )

Answer 32

1. Leveling 2. Balancing

Question 33

What is Process Decomposition?

Answer 33

1. Divide System into a more detailed version * Enterprise Resource System - 1.0 Sale - 1.1 Record Order , ... - 2.0 Production - 2.1 Serve Product , ... - 3.0 Procurement - 3.1 Produce Purchase Order , ... - 4.0 Payroll - 4.1 Record Time Worked , ..

Question 34

List out 3 Correct examples of Data Flows

Answer 34

1. Process to Process 2. Process to External Entity 3. Process to Data Store

Question 35

List out 3 Incorrect examples of Data Flows

Answer 35

1. External Entity to External Entity 2. External Entity to Data Store 3. Data Store to Data Store