Additional Windchill Capabilities > Manufacturing Process Management > Transforming an eBOM into an mBOM > Creating an mBOM > Overview of Generate Downstream Structure Action > Delegates Supporting Generate Downstream Structure Action Framework
  
Delegates Supporting Generate Downstream Structure Action Framework
The following delegate classes support the Generate Downstream Structure action framework:
Preprocessor (BOMGenerationPreProcessDelegate): Out-of-the-box, verifies whether the selected upstream and downstream nodes are equivalent.
Search (BOMGenerationSearchCriteriaDelegate): Out-of-the-box, matches the upstream and downstream structure using custom attributes.
Resolver (BOMGenerationResolverDelegate): Out-of-the-box, adds the matching parts in the downstream structure. It restructures the transferred nodes in the downstream structure based on the defined custom attributes.
Postprocessor (BOMGenerationPostProcessDelegate): Out-of-the-box, creates a log to store the results of the action.
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The Propagate Upstream Changes feature calls the search and resolver delegates to ensure that any customized logic is applied when upstream nodes are propagated downstream. So, any logic that is specific to the Generate Downstream Structure action should be added to the preprocessor or postprocessor delegates. For more information on the Propagate Upstream Changes feature, see Propagating Upstream Changes.