什么是SAP S/4HANA的extension flow

Suppose I have extended MARA with the following field, how could I know whether there are other tables extended automatically?

For example， EPRODUCT is extended automatically as well:

My very first assumption is that any view which has association to E_PRODUCT will also be extended as well. Soon I found I am wrong. The counter-example: A_PRODUCT

In order to get a complete list of extension flow, you have to use query on table DD03L:

146 tables / structures are also extended automatically.

To summarize:

(1) any view which has association to E_PRODUCT will also be extended as well. - WRONG!

(2) any DDIC object which has below structure included will automatically be extended as well:

That is to say, instead of DD03L, you can also use where used list on structure to get the same result:

And how I know the include name PRD_INCL_EEW_PS? From extension registry: