The AP203 Amendment 1 version published in 2000 adds a number of new entities. It also make some changes to existing attribuutes, selects, and enumerations, but does so in a way that is transparent to existing STEP files.

The Amendment adds the new definitions for bounded_pcurve, bounded_surface_curve, founded_item, and founded_item_select. If you were previously using a complex instance of bounded_curve and surface_curve, you should switch your code to use the new bounded_surface_curve definition.

In the following two entities, the 'description' attribute were renamed to 'definition' so that they match the entites used in all of the newer APs. You will need to update any code that calls the old description() access methods:

• alternate_product_relationship
• assembly_component_usage_substitute

In addition, new elements were added to the following selects. Since this is just an addition, you should not need to change any code that uses them:

• date_time_select
• person_organization_select

Finally, the order of elements in the following enumerations and selects were changed. This does not affect any existing code:

• b_spline_curve_form
• b_spline_surface_form
• knot_type
• measure_value
• preferred_surface_curve_representation
• shell
• si_prefix
• si_unit_name
• source
• transition_code
• trimming_preference