= Normalization and design improvements

In my initial DDL design, several entities shared the same attribute names, so I renamed them to make the design clearer and eliminate any ambiguous information.
The changes I made follow the format (relation_name_specification):
content → story_content, chapter_content, comment_content, notification_content, list_content
created_at → user_created_at, story_created_at, chapter_created_at, list_created_at, notification_created_at, like_created_at, comment_created_at, collab_created_at, suggestion_created_at
updated_at → user_updated_at, story_updated_at, chapter_updated_at, list_updated_at, comment_updated_at
name → user_name, genre_name, list_name

After these changes, I obtained the following de-normalized relation:
=== Global Relation
R = {user_id, username, email, user_name, surname, password, user_created_at, 
user_updated_at, story_id, mature_content, short_description, image, story_content, 
story_created_at, story_updated_at, status, chapter_id, chapter_number, chapter_name, 
title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, 
chapter_updated_at, genre_id, genre_name, list_id, list_name, list_content, is_public, 
list_created_at, list_updated_at, added_at, notification_id, notification_content, is_read, 
type, link, notification_created_at, content_type, suggestion_id, original_text, 
suggested_text, accepted, applied_at, suggestion_created_at, suggestion_type, comment_id, 
comment_content, comment_created_at, comment_updated_at, roles, permission_level, 
collab_created_at, like_created_at}

== Functional Dependencies:

- FD1: user_id  → username, email, user_name, surname, password, user_created_at, user_updated_at
- FD2: username → user_id
- FD3: email    → user_id
- FD4: story_id → mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at
- FD5: chapter_id → chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, story_id, chapter_created_at, chapter_updated_at
- FD6: {story_id, chapter_number} → chapter_id
- FD7: genre_id   → genre_name
- FD8: genre_name → genre_id
- FD9: list_id → list_name, list_content, is_public, user_id, list_created_at, list_updated_at
- FD10: notification_id → notification_content, is_read, recipient_user_id, type, link, notification_created_at
- FD11: suggestion_id → original_text, suggested_text, accepted, suggestion_created_at, applied_at, story_id
- FD12:comment_id → comment_content, user_id, story_id, comment_created_at, comment_updated_at
- FD13: {user_id, story_id} → like_created_at
- FD14: {user_id, story_id} → collab_created_at
- FD15:{list_id, story_id} → added_at   -> /

=== Closures
user_id+ = {user_id, username, email, user_name, surname, password,user_created_at, user_updated_at} → Does NOT contain all attributes of R 

username+ = {username, user_id, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

email+ = {email, user_id, username, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

story_id+ = {story_id, mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

chapter_id+ = {chapter_id, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, story_id, chapter_created_at, chapter_updated_at, mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

{story_id, chapter_number}+ = {story_id, chapter_number, chapter_id, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

genre_id+ = {genre_id, genre_name} → Does NOT contain all attributes of R 

genre_name+ = {genre_name, genre_id} → Does NOT contain all attributes of R 

list_id+ = {list_id, list_name, list_content, is_public, user_id, list_created_at, list_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

notification_id+ = {notification_id, notification_content, is_read, recipient_user_id, type, link, notification_created_at} → Does NOT contain all attributes of R 

suggestion_id+ = {suggestion_id, original_text, suggested_text, accepted, suggestion_created_at, applied_at, story_id,  mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

comment_id+ = {comment_id, comment_content, user_id, story_id, comment_created_at, comment_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

{user_id, story_id}+ = {user_id, story_id, like_created_at, collab_created_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

{list_id, story_id}+ = {list_id, story_id, added_at, list_name, list_content, is_public, list_created_at, list_updated_at, mature_content, short_description, image, story_content,user_id, story_created_at, story_updated_at, username, email, user_name, surname, password, user_created_at, user_updated_at} → Does NOT contain all attributes of R 

=== 1NF Check
Every column in the database holds just one value, so there are no lists or multi-value attributes in the cells. There are no repeating columns, each table has a primary key, and all attributes are atomic, so my relations satisfy 1NF.

=== 2NF Check
Every table that has a simple (non-composite) primary key is already in 2NF, so we only need to check the tables that have composite keys.

STATUS {story_id, status} → There are no other attributes, so it satisfies 2NF.

CONTENT_TYPE {notification_id, content_type} → There are no other attributes, so it satisfies 2NF.

SUGGESTION_TYPE {suggestion_id, suggestion_type} → There are no other attributes, so it satisfies 2NF.

LIKES {user_id, story_id} → like_created_at depends on {user_id, story_id} together, so it satisfies 2NF.

COLLABORATION {user_id, story_id} → collab_created_at depends on {user_id, story_id} together, so it satisfies 2NF.

ROLES {user_id, story_id, roles} → There are no other attributes, so it satisfies 2NF.

PERMISSION_LEVEL {user_id, story_id, permission_level} → There are no other attributes, so it satisfies 2NF.

HAS_GENRE {story_id, genre_id} → There are no other attributes, so it satisfies 2NF.

READING_LIST_ITEMS {list_id, story_id} → added_at depends on {list_id, story_id} together, so it satisfies 2NF.

NOTIFY {user_id, story_id, notification_id} → There are no other attributes, so it satisfies 2NF.

NEED_APPROVAL {suggestion_id, story_id, chapter_id} → There are no other attributes, so it satisfies 2NF.

Since there are no partial dependencies in any of the tables, this schema satisfies 2NF.

=== 3NF Check
We checked all FDs where the left side is a primary key, so we can skip those. We only need to check:
FD6: {story_id, chapter_number} → chapter_id → here we can see that there is a UNIQUE constraint on {story_id, chapter_number}, which tells us that it is also a superkey. 
After this we can safely say that the schema satisfies 3NF.