1. Context and Data Flow Diagrams
Ms Sanchez

2. Context and Data Flow Diagrams
The main tools used to pictorially depict how application data and information moves through the system.
The processes that manipulate the data and produce information are named but not fully described.

3. Context and Data Flow Symbols
There are 4 symbols in these types of diagrams.
Entity
Process or System
Data store
Data flow

4. Data flows
Data flows describe the data being transferred. NOT THE PROCESSING!
Uses nouns (naming words) to name data flows.

5. Process or System
The circle represents the whole information processing system or a specific process in the system.
Verbs (actions words) are used to name processes
Nouns (naming words) are used for information systems to indicate their purpose.

6. Entity
People, programs, organisations or other IS that provide data to the system or receive output from the system are external entities.
They are also called: “source” or “destination of data”.
Nouns (naming words) are used to name external entity types

7. Data Store Type of storage is irrelevant.
The name of the data store is placed between the lines and identifies the data it holds.
Nouns are used to name data stores.
A data store represents a set of data records that are unique but have similar characteristics.

8. Context Diagrams
A context diagram is the highest level of the data flow diagram.
It gives a general description of the system.
Indicates the relationship between the system and the rest of the world.
CDs identify and document all the data that flows into and out of the system.
It doesn’t show much detail

9. Context Diagram Example
Bookin g
Nishan’s Restaurant System
Invoic e
Food Suppliers
Diners
Bill
Orders
Food Orders

10. Drawing DFDs Creating Logical DFDs logical DFD of the same processing
2.1
checked
customer order
2.2
customer order
check
customer
order
Check
production
feasibility
accepted order
order
details
2.3
order
commit
resources
resources
used
resources schedule