Chapter 7 : Logical Modelling Flashcards
What is the purpose of Data Flow Diagrams?
- To show the process that data undergo in a system
- To show how data moves and changes through an information system in a graphical
- To produce a logical model of an information system in a simple, direct way
List out 4 Components of DFD
- External Entities / Source & Sink
- Process
- Data Flow
- Data Store
List out 2 type of symbols representing DFD?
- Gane and Sarson Symbols
- Yourdon Symbols
- View symbols at slide 8
What does External Entities / Source & Sink also known as?
- Terminators
What is External Entities / Source & Sink / Terminators?
- 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
What is Source also known as?
- Origin
What is a Source
- An external entity that supplies data
What is a Sink?
- An external entity that receives data
What is Sink also known as ?
- Sink
What is process also known as? ( 2 )
- Bubble
- Transform
What does Process modifies?
- Modifies or change data from one form to another form
- Is named to identify the function it accomplishes
What is the rule for process in a diagram?
- A diagram should have no more than 9 process symbols
What does Data Flow represents?
- Represents the transfer of data among data stores, sources or sinks, and processes
- Line can be curved or straight
What is Data Store?
- A data repository
When is Data Store used?
1.It is used when the system must store data because one or more processes need to use the stored data a later time
What is the rule for Data Store?
- Process may connect to data storesd
What is a Data Flow Diagram ?
- 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
What is a Context Diagram ( DFD ) ?
- Top-level view of the information system
What are the symbols used in Context Diagram?
- One process symbol representing the entire information system
- Has the external entities around the perimeter of the page
- Use data flow to connect the external entities with the process
List out things that I need to identify when drawing context diagram ( 3 )
- Identify Process ( Name of the system )
- Identify External Entities ( Stakeholder )
- Identify Data Flows
List out 6 guidelines for drawing DFD
- 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
- Do no cross lines
- Provide a unique name and reference number for each process
- Ensure that the model is accurate, easy to understand, and meets the needs of its users
List out rules between source to sink in Basic Data Flow Diagram
- 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
List out rules between source ( Entity ) to data store in Basic Data Flow Diagram
- 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
List out rules between Data Store to Sink ( Entity ) in Basic Data Flow Diagram?
- 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 )
List out rules between Data Store to Data Store in Basic Data Flow Diagram?
- 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
What is lower level diagrams also called?
- Child Diagram
What is Child Diagram exploded from?
- Parent Diagram
What is the rules for drawing Low-level Diagrams? ( 2 )
- Leveled
- Also called exploded, partitioned and decomposed
- Drawn in a series of increasingly detailed diagrams until desired degree of detailed is reached
- Balanced
- Maintain consistency among the entire series of diagrams
How many level do we need to create for DFD?
- 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
What are the rules for creating Level 0 DFD
- If same data flows in both directions, I can use a double-headed arrow
- Diagram 0 is an exploded view of Process 0
- Parent Diagram
- Child Diagram
- Process 0
Order Management System
Level 0
DFD
1. Fill Order
2. Create Invoice
3. Apply Payment
What is the next step after creating Level 0 DFD?
- Draw the Lower Level Diagrams
- The level are depend on Process
What is the techniques that Leveling must use? ( 2 )
- Leveling
- Balancing
What is Process Decomposition?
- 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 , ..
List out 3 Correct examples of Data Flows
- Process to Process
- Process to External Entity
- Process to Data Store
List out 3 Incorrect examples of Data Flows
- External Entity to External Entity
- External Entity to Data Store
- Data Store to Data Store
