In reviewing the changes that take place on purchase order records, the reporting team has concluded that the best source for publisher and publication date field data is the MARC record. The MARC record is what populates the inventory_instances table for publisher and publication date, so this is fine to use as well.
The po_lines table in the LDP and Metadb includes data fields for publisher and publication date that may not be populated for all records.
If you need to tie purchase order lines with publisher and publisher date, you can use the derived table po_instance, which connects purchase orders with instances.
Tables that are derived from the po_lines table, such as po_instance, may or may not have the publisher and publication date. The instance_publication derived table has multiples of publisher and publication date. The 1.7 Poppy version of instance_publication uses ordinality, which will help prevent these multiples.