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
{chapter_id, genre_id, list_id, notification_id, suggestion_id, comment_id, status, content_type, suggestion_type, roles, permission_level}+ = {chapter_id, genre_id, list_id, notification_id, suggestion_id, comment_id, status, content_type, suggestion_type, roles, permission_level, 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, like_created_at, collab_created_at, genre_name, list_name, list_content, is_public, list_created_at, list_updated_at, added_at, notification_content, is_read, recipient_user_id, type, link, notification_created_at, original_text, suggested_text, accepted, suggestion_created_at, applied_at, comment_content, comment_created_at, comment_updated_at} → contains all attributes of R → This is the Candidate Key (Primary Key) of R, this is only candidate key because it covers all attributes of R,it's minimal and no alternative exists(every attribute group is independent).
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. The candidate key of R is: CK = {chapter_id, genre_id, list_id, notification_id, suggestion_id, comment_id, status, content_type, suggestion_type, roles, permission_level} since it is the only combination whose closure contains all attributes of R, and no proper subset of it can determine all attributes of R.
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:
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.
Lossless Join Verification
Step 1: Decompose R → USERS + R₁ — common attribute: user_id → primary key of USERS
R₁ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at} Step 2: Decompose R₁ → STORY + R₂ — common attribute: story_id → primary key of STORY
R₂ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at} Step 3: Decompose R₂ → CHAPTER + R₃ — common attribute: chapter_id → primary key of CHAPTER
R₃ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at} Step 4: Decompose R₃ → GENRE + R₄ — common attribute: genre_id → primary key of GENRE
R₄ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, genre_name} Step 5: Decompose R₄ → READING_LIST + R₅ — common attribute: list_id → primary key of READING_LIST
R₅ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, genre_name, list_name, list_content, is_public, list_created_at, list_updated_at} Step 6: Decompose R₅ → NOTIFICATION + R₆ — common attribute: notification_id → primary key of NOTIFICATION
R₆ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, genre_name, list_name, list_content, is_public, list_created_at, list_updated_at, notification_content, is_read, type, link, notification_created_at} Step 7: Decompose R₆ → AI_SUGGESTION + R₇ — common attribute: suggestion_id → primary key of AI_SUGGESTION
R₇ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, genre_name, list_name, list_content, is_public, list_created_at, list_updated_at, notification_content, is_read, type, link, notification_created_at, original_text, suggested_text, accepted, suggestion_created_at, applied_at} Step 8: Decompose R₇ → COMMENT + R₈ — common attribute: comment_id → primary key of COMMENT
R₈ = All attributes of R, except: {username, email, user_name, surname, password, user_created_at, user_updated_at, mature_content, short_description, image, story_content, story_created_at, story_updated_at, chapter_number, chapter_name, title, chapter_content, word_count, rating, published_at, view_count, chapter_created_at, chapter_updated_at, genre_name, list_name, list_content, is_public, list_created_at, list_updated_at, notification_content, is_read, type, link, notification_created_at, original_text, suggested_text, accepted, suggestion_created_at, applied_at, comment_content, comment_created_at, comment_updated_at} Step 9: Decompose R₈ → STATUS + R₉ — common attribute: story_id → primary key of STORY
R₉ = All attributes of R, except: {... same as R₈ ..., status} Step 10: Decompose R₉ → CONTENT_TYPE + R₁₀ — common attribute: notification_id → primary key of NOTIFICATION
R₁₀ = All attributes of R, except: {... same as R₉ ..., content_type} Step 11: Decompose R₁₀ → SUGGESTION_TYPE + R₁₁ — common attribute: suggestion_id → primary key of AI_SUGGESTION
R₁₁ = All attributes of R, except: {... same as R₁₀ ..., suggestion_type} Step 12: Decompose R₁₁ → LIKES + R₁₂ — common attributes: {user_id, story_id} → primary key of LIKES
R₁₂ = All attributes of R, except: {... same as R₁₁ ..., like_created_at} Step 13: Decompose R₁₂ → COLLABORATION + R₁₃ — common attributes: {user_id, story_id} → primary key of COLLABORATION
R₁₃ = All attributes of R, except: {... same as R₁₂ ..., collab_created_at} Step 14: Decompose R₁₃ → ROLES + R₁₄ — common attributes: {user_id, story_id} → primary key of ROLES
R₁₄ = All attributes of R, except: {... same as R₁₃ ..., roles} Step 15: Decompose R₁₄ → PERMISSION_LEVEL + R₁₅ — common attributes: {user_id, story_id} → primary key of PERMISSION_LEVEL
R₁₅ = All attributes of R, except: {... same as R₁₄ ..., permission_level Step 16: Decompose R₁₅ → HAS_GENRE + R₁₆ — common attributes: {story_id, genre_id} → primary key of HAS_GENRE
R₁₆ = All attributes of R, except: {... same as R₁₅ ..., genre_id} Step 17: Decompose R₁₆ → READING_LIST_ITEMS + R₁₇ — common attributes: {list_id, story_id} → primary key of READING_LIST_ITEMS
R₁₇ = All attributes of R, except: {... same as R₁₆ ..., added_at Step 18: Decompose R₁₇ → NOTIFY + R₁₈ — common attributes: {user_id, story_id, notification_id} → primary key of NOTIFY
R₁₈ = {suggestion_id, story_id, chapter_id} — only the attributes of NEED_APPROVAL remain Step 19: Decompose R₁₈ → NEED_APPROVAL (final relation) — common attributes: {suggestion_id, story_id, chapter_id} → primary key of NEED_APPROVAL
R₁₉ = ∅ — all attributes fully decomposed
At every step the common attributes form a primary key in the extracted relation, so the entire decomposition is lossless and no information is lost.
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
We analyze each relation for BCNF violations: USERS(user_id, username, email, user_name, surname, password, user_created_at, user_updated_at) — FD2: username → user_id and FD3: email → user_id exist, but username and email are both superkeys (their closure contains all attributes of USERS). No BCNF violation.
STORY(story_id, ...) — only FD4 applies, story_id is the sole candidate key and the only determinant. No BCNF violation.
CHAPTER(chapter_id, ...) — FD5: chapter_id → all others, FD6: {story_id, chapter_number} → chapter_id. Both chapter_id and {story_id, chapter_number} are candidate keys, so both are superkeys. No BCNF violation.
GENRE(genre_id, genre_name) — FD7: genre_id → genre_name and FD8: genre_name → genre_id. Both are candidate keys, so both are superkeys. No BCNF violation.
READING_LIST(list_id, ...) — only FD9 applies, list_id is the only determinant and is the candidate key. No BCNF violation.
NOTIFICATION(notification_id, ...) — only FD10 applies, notification_id is the only determinant and is the candidate key. No BCNF violation.
AI_SUGGESTION(suggestion_id, ...) — only FD11 applies, suggestion_id is the only determinant and is the candidate key. No BCNF violation.
COMMENT(comment_id, ...) — only FD12 applies, comment_id is the only determinant and is the candidate key. No BCNF violation.
All remaining tables — no non-trivial functional dependencies beyond the primary key. No BCNF violations.
Since every determinant in every relation is a superkey, all relations satisfy BCNF.
BCNF Decomposition
Since no BCNF violations were identified in the BCNF Check, no decomposition is required
Conclusion
After normalization we get same relations from phase 2. So this mean that the database was well modeled.
