We need to do this from the bottom up.

To know these areas, I need to know the base.

If you start constructing service from what you have - bottom-up - you have a very high risk to end up with what you have, not with what your consumers need.

What passes through a portion of C in unit time is the contents of a parallelogram whose base is on C.

In other scenarios, you might develop using a bottom-up approach, in which you would create your entity objects first and then create the database tables from the entities later.