This part of ISO 10303 defines a language by which aspects of product data can be specified. The language is called EXPRESS. This part of ISO 10303 also defines 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 which allow an unambiguous data definition and specification of constraints on the data defined. The following are within the scope: — data types; — constraints on instances of the data types. The following are outside the scope of this part of ISO 10303: — definition of database formats; — definition of file formats; — definition of transfer formats; — process control; — information processing; — exception handling. EXPRESS is not a programming language.