Construction History Model Overview
From WikiSTEP
Solid Model Construction History
Abstract Background Scope Model Overview EXPRESS short listing Implementation and Part 21 File
Vendor feedback from the Construction History Model Workshop in October led to restructuring to a model that vendors believe can be more easily implemented. High-level EXPRESS-G diagrams are given in Figure 1 and Figure 2.
Figure 1 provides representation structures and shows the relationships between key entities. The advanced_brep_shape_representation entity will serve in the exchange as the current result noted earlier, which will help validate the reconstruction of the model in the target system. It is the primary entity for AP 203 Class 6 implementations. A list (sequential) of geometric entities, represented by operation_sequence and created as an integral part of the construction history, is captured in the construction_history_shape_representation. Geometric elements represented by imported_reference_element is a set of entities in the model that may no longer exist (e.g., an edge that was filleted), or that were modified (e.g., faces associated with a fillet, or a face where a hole entrance was created). This is an important structure to assist the post-processor developer in re-creating the history in the target system, thus enabling editing of the model. The functional_parametric_history_model entity is a ‘collector’ of relevant information that is intended to be sent as part of the construction history. One attribute is the current_result, while another is modeling_operations represented by construction_history_shape_representation; the third attribute is the imported_reference_element noted earlier.
