ISO 10303-21

ISO 10303 can represent 3D objects in computer-aided design (CAD) and related information.

The Industry Foundation Classes and earlier CIMSteel Integration Standard (CIS/2) define an EXPRESS schema for building information modeling data and specify ISO 10303-21 as an exchange encoding.

This graph shows the entity instances and the references between them in a file representing a solid model of a cylinder.

Possibly the only advantage of STEP files is that they are widely adopted in many CAD software.

On the other hand, its format, and specially the EXPRESS data modelling language has a few disadvantages:[opinion]