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

We analyze the global relation R with candidate key: CK = {chapter_id, genre_id, list_id, notification_id, suggestion_id, comment_id, status, content_type, suggestion_type, roles, permission_level} Since CK is composite, we check R for partial dependencies — cases where a proper subset of CK determines a non-prime attribute:

chapter_id → chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, story_id, chapter_created_at, chapter_updated_at — partial dependency, violates 2NF genre_id → genre_name — partial dependency, violates 2NF list_id → list_name, list_content, is_public, user_id, list_created_at, list_updated_at — partial dependency, violates 2NF notification_id → notification_content, is_read, type, link, notification_created_at — partial dependency, violates 2NF suggestion_id → original_text, suggested_text, accepted, suggestion_created_at, applied_at, story_id — partial dependency, violates 2NF comment_id → comment_content, user_id, story_id, comment_created_at, comment_updated_at — partial dependency, violates 2NF

R is in 1NF but NOT in 2NF. We decompose R by extracting each group of partially dependent attributes into its own relation, keeping the determinant as the primary key. The story and user attributes are resolved transitively through the decomposition of chapter_id → story_id and story_id → user_id.

2NF Decomposition

After decomposition we verify that every resulting relation satisfies 2NF: USERS(user_id, username, email, user_name, surname, password, user_created_at, user_updated_at) → simple primary key user_id, so it satisfies 2NF. STORY(story_id, mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at) → simple primary key story_id, so it satisfies 2NF. CHAPTER(chapter_id, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, story_id, chapter_created_at, chapter_updated_at) → composite candidate key {story_id, chapter_number} exists, but all other attributes depend on the full key, not a subset. No partial dependencies, so it satisfies 2NF. GENRE(genre_id, genre_name) → simple primary key genre_id, so it satisfies 2NF. READING_LIST(list_id, list_name, list_content, is_public, user_id, list_created_at, list_updated_at) → simple primary key list_id, so it satisfies 2NF. NOTIFICATION(notification_id, notification_content, is_read, type, link, notification_created_at) → simple primary key notification_id, so it satisfies 2NF. AI_SUGGESTION(suggestion_id, original_text, suggested_text, accepted, suggestion_created_at, applied_at, story_id) → simple primary key suggestion_id, so it satisfies 2NF. COMMENT(comment_id, comment_content, user_id, story_id, comment_created_at, comment_updated_at) → simple primary key comment_id, so it satisfies 2NF. 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) → like_created_at depends on {user_id, story_id} together, so it satisfies 2NF. COLLABORATION(user_id, story_id, collab_created_at) → 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) → 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 resulting tables, this schema satisfies 2NF.

3NF Check

We analyze each relation obtained from the 2NF decomposition for transitive dependencies.

USERS(user_id, username, email, ...) — FD2: username → user_id and FD3: email → user_id exist, but username and email are both candidate keys, not non-prime attributes. No transitive dependency. STORY(story_id, ..., user_id, ...) — user_id is a non-prime attribute, but within this relation user_id does not determine any other attribute. No transitive dependency. CHAPTER(chapter_id, ..., story_id, ...) — story_id is a non-prime attribute, but within this relation story_id does not determine any other attribute. No transitive dependency. GENRE(genre_id, genre_name) — both attributes are candidate keys. No transitive dependency. READING_LIST(list_id, ..., user_id, ...) — user_id is a non-prime attribute, but within this relation user_id does not determine any other attribute. No transitive dependency. NOTIFICATION, AI_SUGGESTION, COMMENT — simple primary keys, no non-prime attribute determines another. No transitive dependencies. All remaining tables — no non-prime attributes at all, or single non-prime attribute depending on the full composite key. No transitive dependencies.

Since no transitive dependencies were found in any relation, all relations already satisfy 3NF.

3NF Decomposition

Since no transitive dependencies were identified in the 3NF Check, no decomposition is required.

BCNF Check

1. USERS(user_id, username, email, user_name, surname, password,

user_created_at, user_updated_at) → satisfies BCNF

2. ADMINS(user_id) → satisfies BCNF

3. REGULAR_USER(user_id) → satisfies BCNF

4. WRITER(user_id) → satisfies BCNF

5. STORY(story_id, mature_content, short_description, image, story_content, user_id, story_created_at, story_updated_at) → satisfies BCNF
6. STATUS(story_id, status) → satisfies BCNF
7. CHAPTER(chapter_id, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, story_id, chapter_created_at, chapter_updated_at) → satisfies BCNF
8. GENRE(genre_id, genre_name) → satisfies BCNF
9. READING_LIST(list_id, list_name, list_content, is_public, user_id, list_created_at, list_updated_at) → satisfies BCNF
10. NOTIFICATION(notification_id, notification_content, is_read, recipient_user_id, type, link, notification_created_at) → satisfies BCNF
11. CONTENT_TYPE(notification_id, content_type) → satisfies BCNF
12. AI_SUGGESTION(suggestion_id, original_text, suggested_text, accepted, suggestion_created_at, applied_at, story_id) → satisfies BCNF
13. SUGGESTION_TYPE(suggestion_id, suggestion_type) → satisfies BCNF
14. LIKES(user_id, story_id, like_created_at) → satisfies BCNF
15. COMMENT(comment_id, comment_content, user_id, story_id, comment_created_at, comment_updated_at) → satisfies BCNF
16. COLLABORATION(user_id, story_id, collab_created_at) → satisfies BCNF
17. ROLES(user_id, story_id, roles) → satisfies BCNF
18. PERMISSION_LEVEL(user_id, story_id, permission_level) → satisfies BCNF
19. HAS_GENRE(story_id, genre_id) → satisfies BCNF
20. READING_LIST_ITEMS(list_id, story_id, added_at) → satisfies BCNF
21. NOTIFY(user_id, story_id, notification_id) → satisfies BCNF
22. NEED_APPROVAL(suggestion_id, story_id, chapter_id) → satisfies BCNF

Conclusion

After normalization we get same relations from phase 2. So this mean that the database was well modeled.