As with bill of materials (BOM) in drawing documents, the BOM Structure property defines the status of each component in the BOM table: Normal, Phantom, Reference, Purchased, and Inseparable. Tube and pipe components typically follow the default BOM structure. Conduit parts and fittings from the Content Center that make up routes and runs are set to Purchased. The master runs assembly, rigid route sketches, hose splines, and hose assemblies do not have distinct line items in bill of materials so they are set to Phantom.
However, you can override the default BOM structure to meet specific design needs. For instance, you can modify the BOM structures so that you can create and export the BOM information for specific routes and runs. When a component has a BOM Structure of Reference, the BOM treats the component and all its direct and indirect children as if they do not exist. All child components, that are a part of a Reference component, are excluded from quantity, mass, or volume calculations, regardless of their own BOM Structure value.