Limiting Values In An Object Property?

I have a class called Item which contains all the information about all parts, finished goods, in process parts (parts made on site), purchased parts, and raw materials.

I have a Bill of Materials table which has the following columns (reflected in the BOM class)

ParentItem
ChildItem
ChildItemQty

Parent Items can only be Items which have subcomponents.

Child Items can be parts that are made on site, purchased parts that are bought ready made from other companies, or raw materials used to make a part that is made on site.

Parent Items and child Items both inherit the Items class.

I will limit the Parent item class to only items that are in the parent column of the BOM table. I believe I can limit that by doing a quick look up on a view which only shows the parent items.

I will limit the Child Item Class to only items that are in the child column of the BOM table. Same method to limit it by doing a quick look up on a view that shows only the child items.

That way, an instance of the BOM class will have all the detail information about any of it's components available whenever I need them.