Creo Options Modeler > References > Data Management > Managing Parts and Documents > Managing Bulk Items > About Using the External Simplified Representation and BOM in Windchill
  
About Using the External Simplified Representation and BOM in Windchill
Use External Simplified Representations to store only the required sub-assemblies without modifying the original assembly. The use of external simplified representations (ESRs) minimizes the risk of accidental modifications to the top-level assemblies.
You can save simplified representations as a separate ESR assembly file. You can also check out and check in the external simplified representations in the active workspace.
 
* To use ESRs that were created in Pro/ENGINEER Wildfire 3.0 or earlier releases in Pro/ENGINEER Wildfire 4.0, you must explicitly save the ESRs in Pro/ENGINEER Wildfire 4.0 before you use them.
While using external simplified representations in an assembly, you can see the structure of that external simplified representation with all its dependencies. You can view this information on the Details page in the workspace by clicking Structure. The Details page is refreshed to display the Model Structure Report table. The Model Structure Report is different than the Model Tree structure, as the Model Structure Report does not show the excluded objects or subassemblies. If you exclude a single component from a subassembly, the entire subassembly is not displayed in the Model Structure Report.
 
* You cannot edit the ComponentId, CAD Feature ID, and CAD Feature Number in the Model Structure Report.
Bill Of Material (BOM)
The Creo application identifies the external simplified representations dependencies in the assembly and also lists these dependencies in a BOM. The BOM serves as a convenient way to view a summary of the assembly. You can view, print, or save this BOM to a disk. The BOM lists the total quantity of each component included in the assembly. This quantity of a component is represented as a sum of multiple occurrences of that component in the assembly.
Using Windchill, you can generate a BOM by clicking for single level BOM or by clicking for multi level BOM on the Model Structure Report in the workspace.
With a Windchill server, you can also see the quantity of each component included in the assembly in the Model Structure Report from the Details page. While using the external simplified representations, the BOM lists only the components and subassemblies, which are not excluded.
For more information on viewing the structure information and creating a BOM using the Windchill user interface, click in the Windchill HTML user interface.