This part of ISO 10303 defines a language by which an instance of (part of) a universe of discourse can be displayed. It also provides a formal description method for supporting the specification of abstract test cases. The language is called EXPRESS-I. It is a companion language to EXPRESS which is specified in ISO 10303-11.

EXPRESS-I is an instantiation language for a conceptual schema language as defined in ISO TR 9007, and the particular conceptual schema language that formed the starting point for EXPRESS-I was EXPRESS. The EXPRESS-I language provides for the display of the state of the objects belonging to a universe of discourse and the information units pertaining to those objects.

The following are within the scope:

• display of instances of schemas;
• display of instances of types and entities;
• abstract test case data;
• mapping from EXPRESS schemas and data types to EXPRESS-I instances.

The following are outside the scope of this part of ISO 10303:

• mapping from other (conceptual schema) languages to EXPRESS-I;
• definition of database formats;
• definition of file formats;
• definition of transfer formats;
• process control;
• information processing;
• exception handling.

EXPRESS-I is not a programming language.