vocabulary JoinEquality;

/*
 * Value Types
 */
Event Id is written as Auto Counter;
Number is written as Unsigned Integer(16);
Reserve is written as String(20);
Row is written as Char(2);
Venue Id is written as Auto Counter;

/*
 * Entity Types
 */
Event is identified by its Id;

Venue is independent identified by its Id;
Event is held at one Venue;

Seat is independent identified by Venue and Reserve and Row and Number where
	Seat is at one Venue,
	Seat is in one Reserve,
	Seat is in one Row,
	Seat has one Number;

Ticket is identified by Event and Seat where
	Ticket is for one Event,
	Ticket is for one Seat;

/*
 * Constraints:
 */
Ticket is for Seat that is at Venue
	if and only if
	Ticket is for Event that is held at Venue;