The traditional or structured approach to design

1. Data flow diagrams

Graphical system model that shows all main requirements for an information system in one diagram.

Typical data flow symbols:
Process: step-by-step instructions that followed to transform input to output.

Data flow: data flowing from place to place, such as an input or output to a process.

External agent: the source or destination of data outside the system.

Data store: data at rest, being stored for late use, usually corresponded to a data entity in a ERD.

Real-time link: communication back and forth between an external agent and a process as the process is executing.

Abnormal in DFD:
Black hole process: process that just have the input.
White hole process: process that just have the output.
Cannot create output from the input.

High-level diagrams provide general view of the system.
Low-level diagrams provide detail vies of the system.
Different views are called levels of abstraction.

Physical model and logical model:
Logical model: assumes implementation in prefect technology, does not tell how system is implemented.
Physical model: describe assumptions about implementation technology, developed in the last stage of design or in early design.

Consistency rule:
All data flows into a process:
a. Must flow out of the process or
b. Be used to generate data that flows out of the process.
All data flows out of a process:
a. Have data that flowed into the process or
b. Have been generated from data that flows into the process.

2. Modules form IE may supplement DFD:
a. Process decomposition diagram: how process on multiple DFD levels is related.
b. Process dependency diagram: emphasizes interaction with store entities.
c. Location diagram: geographic where system used.
d. Activity-location matrix
e. Activity-data matrix.