Understanding Hierarchy

There is a three-tiered hierarchy - portfolio, accounts, and merchants (MIDs), in descending order. Portfolios and accounts can both create meta keys, and the key can be assigned to a select group in the hierarchy or to all nodes in the hierarchy.
In the diagram below, if the portfolio (portfolio1) assigns a meta key to all merchants, every merchant in the diagram is assigned the key. However if an account (account1) assigns a key to all merchants, only merchants below it are assigned the key (merchant1, merchant2).