EVENT

The type of events that drive the execution of regulative rules. An event records who did what, and when.

Syntax

-- As a type
EVENT partyType actionType

-- As a constructor
EVENT party action timestamp

Purpose

A DEONTIC party action value describes obligations; a list of EVENT party action values describes what actually happened. Feeding events to a contract (via #TRACE ... WITH ... or the EVALTRACE function) advances the contract state and determines whether obligations are fulfilled or breached.

The EVENT constructor takes three arguments:

Argument	Type	Meaning
`party`	`party`	Who performed the action
`action`	`action`	What was done
`timestamp`	`NUMBER`	When it happened (contract time)

Examples

DECLARE Person IS ONE OF Seller, Buyer
DECLARE Action IS ONE OF
  delivery
  payment HAS amount IS A NUMBER

-- Events in a #TRACE directive
#TRACE saleContract AT 0 WITH
  PARTY Seller DOES delivery AT 2
  PARTY Buyer DOES payment 100 AT 5

-- Events constructed explicitly for EVALTRACE
#EVAL EVALTRACE saleContract 0 (LIST (EVENT Seller delivery 2), (EVENT Buyer (payment 100) 5))

EVALTRACE has type DEONTIC party action → NUMBER → LIST OF EVENT party action → DEONTIC party action: it advances the contract from the given start time through the events and returns the residual contract state.

WAIT UNTIL

`WAIT UNTIL` (a builtin, type NUMBER → EVENT a b) produces a synthetic event that matches no party and no action — it is only relevant for its timestamp. Use it to let time pass and trigger deadline expiry without any party acting:

#TRACE saleContract AT 0 WITH
  PARTY Seller DOES delivery AT 2
  (`WAIT UNTIL` 10)

Notes

EVENT is a builtin: the name serves both as the type (EVENT party action) and as its constructor. In current releases the constructor resolution takes precedence, so use EVENT to build values (and in LIST OF EVENT ... positions inside EVALTRACE calls) rather than as a standalone parameter type annotation.
Events whose party or action matches nothing in the contract simply do not discharge any obligation; only their timestamps advance contract time (this is exactly how `WAIT UNTIL` works).