Generalization, Specialization and Aggregation in DBMS

What is Generalization

In generalization we combine lower level entities to form a higher level entity. Thus its clear that it follows a bottom up approach.

Example –

In a bank there are two different types of accounts – Current and Savings, combine to form a super entity Account.

It thus follows system like classes, like super-classes and sub-classes right ?

It may also be possible that the higher level entity may also combine with further entity to form a one more higher level entity.