Please specify how the variable is linked to the header

https://vscode.dev/github/sdmx-twg/wp-sdmx-dpm/blob/main/docs/models-relationships/02_data_definition/03_detailed_mapping_rules.md#L228-L229

The current header version entity includes an optional propertyid and an optional keyvariablevid.
Is propertyid used for facts and attributes?
Is keyvariableid used for keys?