Product-Level Relationships 

Each type of product-level relationship corresponds to a real-world relationship between main table records and/or non-main table records, as summarized in the table below and described in the following sections.

Type	Table(s)	Examples
Sibling	Main	●      Cross-sells (related products) ●      Interchange products (all equivalent)
Parent/Child	Main/Main	●      Assemblies and components (“SKU of SKUs”) ●      Up-sells ●      Accessories ●      Consumables ●      Replacements ●      Supercessions ●      Interchange products (one preferred)
	Main/Subtable	●      Kits and parts (“SKU of non-SKUs”) ●      Cross-reference part numbers
	Subtable/Main	●      Bundles (“non-SKU of SKUs”) ●      Interchange product groups
	Subtable/Subtable	●      Parts and subparts (“kits of kits”) ●      Bill of materials
	Subtable1/Subtable2	●      Interchange part number groups

The tables of a parent/child relationship can be of type Main, Flat, Hierarchy, or Qualified (but not of type Taxonomy).

If a relationship embodies both sibling and parent/child data, and/or the parent/child data relates records both within the main table and between the main table and one or more subtables, you can create multiple independent product relationships to store the data and then combine them at the presentation layer into a hybrid relationship.

An interchange is an alternate product that can be substituted for a given product, both of which are main table records in the repository. If the interchange products records are all completely equivalent, use a sibling product relationship to represent this information; if one of the group of interchange products is the “preferred” product, use a parent/child relationship. By contrast, a cross-reference is an alternate part number for a given product that can be used to find the main table record but that is not itself a record; use a parent/child relationship (main/subtable) to represent this information. (When the cross-reference part numbers come from a known set of alternate sources, you can instead use a qualified table to represent this information, which improves the ability to search by the cross reference part number information.)