The following diagram represents the metadata XML files used for a Fusion web application:

Note : The above is an excerpt from : Jobinesh : Oracle ADF Real World Developer Guide

What happens when you execute an entity-based view object?

ViewObject vo = applicationModule.findViewObject("Departments");

vo.execute();//execute view object to fetch rows

Row row=vo.first();//Move to the first row in the row set

The following sequence diagram highlights how the business components interact

with one another to query the database:

Note : The above content is from : Jobinesh  : Oracle ADF Real World Developer Guide a fantastic book on ADF.

Just shared the above for reference to others.