# Entity Model --- **Document Version:** 1.0 **Project:** Student Bazaar **Document Type:** Entity Model Specification **Status:** Approved **Last Updated:** 28 June 2026 **Author:** Nemmi Tangha --- # 1. Purpose This document defines the core entities of Student Bazaar and describes their responsibilities, relationships, and business rules. Each entity represents a logical component of the system and will later be implemented as one or more database tables using SQLAlchemy and MySQL. This document serves as the foundation for: * Entity Relationship Diagram (ERD) * Database Schema * SQLAlchemy Models * API Design * Business Logic --- # 2. Entity Overview Student Bazaar is divided into the following domains: * Authentication * Marketplace * Communication * Negotiation * Meet-up Scheduling * Notifications * Administration * Premium Services * Analytics --- # 3. Authentication Entities ## User ### Purpose Represents every registered account within the system. A single Student account can act as both buyer and seller. A Super Admin manages the platform. ### Relationships * One User creates many Listings. * One User sends many Messages. * One User receives many Notifications. * One User creates many Offers. * One User creates many Reports. * One User owns zero or one Premium Subscription. --- ## Email Verification ### Purpose Stores email verification requests and verification tokens. ### Relationships * Belongs to one User. --- ## Password Reset Token ### Purpose Stores secure password reset requests. ### Relationships * Belongs to one User. --- # 4. Marketplace Entities ## Category ### Purpose Organizes product listings into logical groups. Examples include: * Electronics * Books * Furniture * Clothing * Accessories ### Relationships * One Category contains many Listings. --- ## Listing ### Purpose Represents a product offered for sale. A listing includes: * Product Information * Price * Status * Expiration * Seller ### Relationships * Belongs to one User. * Belongs to one Category. * Has many Images. * Has many Offers. * Has one Conversation. * Has many Favorites. * Has many Views. * Has many Reports. --- ## Listing Image ### Purpose Stores images belonging to a product listing. Business Rule: Each listing must contain: * Minimum 1 image * Maximum 7 images ### Relationships * Belongs to one Listing. --- ## Favorite ### Purpose Stores products saved by students. ### Relationships * Belongs to one User. * References one Listing. --- # 5. Negotiation Entities ## Offer ### Purpose Represents the current negotiation between buyer and seller. Supports: * Initial Offer * Counter Offer * Accepted Offer * Rejected Offer ### Relationships * Belongs to one Listing. * Created by one User. --- ## Offer History ### Purpose Maintains the complete negotiation history. No offer should be permanently overwritten. Every price proposal is preserved. ### Relationships * Belongs to one Offer. --- # 6. Communication Entities ## Conversation ### Purpose Represents a chat related to one specific listing. Business Rules: * One conversation per listing. * Chat activates only after both users exchange their first message. * Free conversations contain 10 messages. * Rewarded advertisements unlock 5 additional messages. * Premium users have unlimited messaging. ### Relationships * Belongs to one Listing. * Connects two Users. * Contains many Messages. --- ## Message ### Purpose Stores messages exchanged during conversations. ### Relationships * Belongs to one Conversation. * Sent by one User. --- # 7. Meet-up Entity ## Meet-up ### Purpose Stores agreed meeting information after an offer is accepted. Students may: * Suggest Date * Suggest Time * Suggest Location * Accept * Reject * Reschedule ### Relationships * Belongs to one accepted Offer. --- # 8. Notification Entity ## Notification ### Purpose Stores user notifications. Examples include: * New Message * New Offer * Counter Offer * Offer Accepted * Meet-up Scheduled * Listing Expiring * Report Update * Premium Reminder ### Relationships * Belongs to one User. --- # 9. Administration Entities ## Report ### Purpose Stores reports submitted by students. Reasons include: * Fake Listing * Spam * Fraud * Harassment * Inappropriate Images ### Relationships * Created by one User. * References one Listing or another User. --- ## Advertisement ### Purpose Stores advertisements displayed throughout the platform. Supports: * Banner Ads * Rewarded Ads ### Relationships Managed by the Super Admin. --- ## Premium Subscription ### Purpose Stores premium membership information. Tracks: * Subscription Status * Start Date * Expiration Date ### Relationships Belongs to one User. --- ## Super Admin Log ### Purpose Records important administrative actions. Examples: * User Suspension * Listing Removal * Report Resolution * Advertisement Updates ### Relationships Created by one Super Admin. --- # 10. Analytics Entities ## Listing Analytics ### Purpose Basic marketplace analytics are stored directly within the `listings` entity. Current analytics include: - View Count - Favorite Count - Offer Count These values support: - Seller Dashboard - Marketplace Statistics - Popular Listings Future versions may introduce a dedicated analytics module if detailed event tracking becomes necessary. ### Relationships References one Listing. --- # 11. Entity Relationships Summary The core relationships include: * User → Listings (1:M) * User → Offers (1:M) * User → Messages (1:M) * User → Notifications (1:M) * User → Reports (1:M) * User → Favorites (1:M) * Category → Listings (1:M) * Listing → Images (1:M) * Listing → Offers (1:M) * Listing → Favorites (1:M) * Listing → Reports (1:M) * Listing → Views (1:M) * Listing → Conversation (1:1) * Conversation → Messages (1:M) * Offer → Offer History (1:M) * Accepted Offer → Meet-up (1:1) --- # 12. Business Rules The following business rules apply: * Every listing belongs to exactly one student. * Every listing must contain between one and seven images. * Every conversation belongs to one listing. * One listing can have only one active conversation between a specific buyer and seller. * Meet-ups can only be scheduled after an offer is accepted. * Student Bazaar never processes payments. * Premium users receive unlimited messaging. * Free users receive ten messages per conversation. * One rewarded advertisement unlocks five additional messages. --- # 13. Future Entities Future versions may introduce additional entities including: * Payment Transactions * AI Recommendations * QR Verification * College Verification * Delivery Tracking * Mobile Devices * Push Notification Tokens These entities are intentionally excluded from Version 1. --- # 14. Conclusion The entities defined in this document represent the complete logical data model for Student Bazaar Version 1. These entities will be translated into a normalized MySQL schema and SQLAlchemy models while preserving the relationships and business rules described in this document.