Data structure diagram

The basic graphic notation elements of DSDs are boxes which represent entities.

In DSDs, attributes are specified inside the entity boxes rather than outside of them, while relationships are drawn as boxes composed of attributes which specify the constraints that bind entities together.

DSDs differ from the E–R model in that the E–R model focuses on the relationships between different entities, whereas DSDs focus on the relationships of the elements within an entity.

There are several styles for representing data structure diagrams, with the notable difference in the manner of defining cardinality.

The model is named after database pioneer Charles Bachman, and mostly used in computer software design.