This part of ISO 10303 specifies a language by which aspects of product data can be defined. The language is called EXPRESS.
This part of ISO 10303 also specifies a graphical representation for a subset of the constructs in the EXPRESS language. This graphical representation is called EXPRESS-G.
EXPRESS is a data specification language as defined in ISO 10303-1. It consists of language elements that allow an unambiguous data definition and specification of constraints on the data defined.