1. The transformation of a nested relation into 1NF is called unnesting.

2. Example. To complete unnest the doc relation, we have

select name, A as author, date.day, date.month, date.year, K as keyword
from doc as B, B.author-list as A, B.keyword-list as K

3. The reverse operation of transformation of a 1NF relation into a nested relation is called nesting.

4. Example. To nest the relation at-doc on the attribute keyword, we have

select title, author, (day, month, year) as date, set(keyword) as keyword-list
from at-doc
groupby title, author, date
This wil generate the following table.

5. Example. To convert at-doc back to the nested table doc, we have
select title, set(author) as author-list, (day, month, year) as date, set(keyword) as keyword-list
from at-doc
groupby title, date