ISO 10303 specifies a language by which aspects of product data can be defined. The language is called EXPRESS. ISO 10303-11:2004 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. The following are within the scope of ISO 10303-11:2004: 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.