= Entity-Relationship Model v.1 =

'''Diagram'''

[[Image(ERModel_v1.png)]]

'''Data requirements'''

=== Entities ===

==== Users ====
Represents the users of the system who can make room reservations or manage the system.

 * '''Candidate keys''': username, email  
 * '''Primary key''': user_id

 * '''Attributes''':
  * user_id – integer, required
  * username – text, required, unique
  * email – text, required, unique
  * role – text, required (user/admin)

==== Rooms ====
Represents rooms that can be reserved in the system.

 * '''Candidate keys''': room_number  
 * '''Primary key''': room_id

 * '''Attributes''':
  * room_id – integer, required
  * room_number – text, required, unique
  * capacity – integer, required
  * type – text, required (classroom, office, meeting room)

==== Reservations ====
Represents reservations made by users for specific rooms and time intervals.

 * '''Candidate keys''': (room_id, start_time, end_time)  
 * '''Primary key''': reservation_id

 * '''Attributes''':
  * reservation_id – integer, required
  * start_time – datetime, required
  * end_time – datetime, required
  * user_id – integer, required
  * room_id – integer, required

=== Relationships ===

 * '''Users – Reservations''': One user can create multiple reservations, but each reservation is created by exactly one user.
 * '''Rooms – Reservations''': One room can be reserved multiple times, but each reservation refers to exactly one room.

== Entity-Relationship Model History ==

 * '''v1''' – Initial ER model created according to the project requirements.