Logical Modelling

To show processes data undergo, how data moves/changes, and to produce a logical model of a system.

External Entities, Processes, Data Flows, and Data Stores.

Terminators.

A person, department, organization, or system that provides or receives data.

Use the singular form of the name.

Bubble or transform.

A function that modifies or changes data from one form to another.

An active verb followed by a singular noun (e.g., "Calculate Pay").

Nine.

The transfer of data among data stores, sources/sinks, and processes.

Adjectives + singular noun (e.g., "Customer Order").

All flow lines must be labeled.

A data repository used to store data for later use by processes.

Only processes.

Plural name with adjectives and a noun (e.g., "Customer Records").

The scope of a system, its boundaries, external entities, and major information flows.

One (representing the whole system).

No.

Identify the process, external entities, and data flows.

Fit on one page, use unique names, don’t cross lines, give each process a unique name/number, and ensure clarity.

Breaking down diagrams into increasing detail.

Ensuring input/output flows in parent diagrams match their child diagrams.

Child diagrams.

An exploded view of Process 0 from the context diagram.

Identify processes, data flows to/from entities, and data stores.

Detailed view of a specific process from a higher-level diagram.

Black Hole, Miracle, and Grey Hole.

A process with inputs but no outputs.

A process with outputs but no inputs.

A process with outputs larger than what inputs could produce.

Data going directly from source to store or source to sink without passing through a process.