Data store

How to read it

Yourdon defines a store as a collection of data at rest, usually named with the plural of what flows in and out of it, such as ORDERS. Once a system is built, he writes, stores typically exist as files or databases. The UKHSA guidance gives horizontal parallel lines for data storage in Yourdon and DeMarco’s notation and open-ended rectangles in Gane and Sarson’s, and Notre Dame’s guide describes either shape as a repository where data is kept for later retrieval or processing.

Also searched as: data flow diagram data store, data store symbol, dfd database, dfd data store, dfd parallel lines, open-ended rectangle dfd.

Numbering

A number such as D1 beside the name only tells one store from another on the diagram, Yourdon explains. His own convention leaves stores unnumbered and numbers the processes.

Look-alikes

A flowchart cylinder also stands for stored data, and a BPMN data object, a page with a folded corner, for information a step uses. An external entity is a closed rectangle.