== ERModel Current version
== Diagram ==
[[Image(ERModel_v01.png)]]
== Data requirements == 
=== ENTITIES ===
{{{User}}}
[[BR]]
Represents every person using the platform: buyers, sellers, and administrators. It is needed to authenticate users, assign roles, and link their actions (listings, reviews, notifications, ownership of animals). It is modeled as a single entity with a role attribute instead of separate tables for buyers/sellers/admins, because one person can play multiple roles over time.
[[BR]]
'''[[span(style=color: #E30B5C, Candidate keys: )]]'''
* {{{user_id}}} – surrogate numeric identifier (chosen primary key).
* {{{username}}} – natural key, must be unique, but can change in the future.
* {{{email}}} – also unique, but might change and can be reused if a user is deleted.
{{{user_id}}} is chosen as PK because it is stable, short, and independent of business rules.
[[BR]]
'''[[span(style=color: #E30B5C, Attributes: )]]'''
* {{{user_id}}} – numeric, required. Auto-generated positive integer; primary key.
* {{{username}}} – text, required. Unique; max length ~30; only letters, digits and some symbols.
* {{{role}}} – text, required. Limited set of values: {ADMIN, USER, GUEST}; implemented as enum.
* {{{fullname}}} – text, required. Free-text full name.
* {{{name}}} – text, required. First name; max length ~50.
* {{{surname}}} – text, required. Last name; max length ~50.
* {{{email}}} – text, required. Must be unique; email format validation.
* {{{created_at}}} – datetime, required. Automatically set when the account is created.
== ERModel History