The ISO and ASME standards provide a rich set of tolerance modifiers that are supported with new types in ISO 10303-47. The use of extensible types supports future extensions to ISO 10303-47 as the ISO and ASME standards evolve. The extensible ENUMERATION type geometric_tolerance_modifier may be applied to dimensions or to geometric properties. In some cases, the ASME or ISO requirement is satisfied by the name of the entity type to which the tolerance is applied instead of by a specific ENUMERATION value.

Upward compatibility and deprecation

The information model created for the first edition of ISO 10303-47 was based on industrial standards and practices that were understood to be necessarily incomplete due to the state of the art and practice.  In some cases the structure of the first edition did not permit extensions and a parallel structure was put in place in the second edition to support continued use of current interfaces. Consequently, those first edition ENTITY types that did not permit extensions have been deprecated in the second edition of ISO 10303-47, and over time it is expected that interface software will migrate to the new structures. The common_datum has been replaced with datum_reference_compartment where the base is a common_datum_list because the common_datum was limited to only two datum whereas the current edition of ISO 5459 requires that a common datum may be composed of more than two datum. The datum_reference has been replaced with a datum_system together with datum_reference_compartment and as needed instances of datum_reference_element. In the first edition of ISO 10303-47 datum system was not explicitly modeled; consequently there was no mechanism to associate a coordinate system with that implicit datum system. The referenced_modified_datum has been replaced with datum_reference_compartment or datum_reference_element because the referenced_modified_datum is a subtype of datum and the modifiers are now located on general_datum_reference. The dimension_related_tolerance_zone_element was unused and that ENTITY type can only specify a dimensional_location which limited its ability to meet the new requirements. With the introduction of dimensional_size and dimensional_location into the select geometric_tolerance_target, geometric_tolerance can directly call out dimensional_size and dimensional_location providing a replacement for dimension_related_tolerance_zone_element. The modified_geometric_tolerance only allowed for one modifier, a limit_condition, which did not meet the new requirements; consequently modified_geometric_tolerance was replaced with geometric_tolerance_with_modifiers which supports an extensible set of geometric_tolerance_modifiers.

EXPRESS

lots of code.

An exchange scenario

This is an example of an exchange scenario involving CAD-CAD for a “between specification”. Figure 10 is an illustration from a CAD system of the example. Only the instance data for the “between specification” will be considered in this example. The datum feature and profile tolerance are excluded.