Transaction process time expressions

Time expressions can be used both with transitions and notifications to delay the execution. The Flex transaction engine exposes a set of timepoints that you can tie delays to as well as a small set of functions to further control the exact timing. The basic structure of a time expression is a map from function name to a list (vector) of function parameters: {:fn/function-name [function-param1 function-param2]}. For example: {fn/timepoint [:time/booking-end].

When a delayed transition or notification is scheduled, it will execute at the resulting time. However, if the transition moves forward before the scheduled moment, the operation is automatically cancelled. This way you can send a reminder notification or schedule an automatic cancellation after a certain time period that will be executed only in the case that nobody takes action before that. Also, if the scheduled time is in the past the operation will execute immediately. By wrapping the time expression with :fn/ignore-if-past you can instead ignore operations when the scheduled time is in the past.

Note that your transaction process can have several automatic transitions scheduled for a state, but only one automatic transition executed for a state. You may have e.g. one automatic transition scheduled to execute 1 day after first entering the state, and another scheduled to execute 7 days before a booking starts. The transition that gets executed is the one whose time point is matched first. However, if the first automatic transition fails for some reason, no further automatic transitions get executed from the state.

To learn more how to use time expressions in the transaction process, see the Transaction process format reference article.

Time functions

Fn	Arguments	Description	Example
:fn/timepoint	timepoint name + timepoint args (if any)	Returns the timestamp of a timepoint in the process.	{:fn/timepoint [:time/first-entered-state :state/state-name]}
:fn/period	Period expression, string	A timespan that can be added or substracted.	{:fn/period ["PT15M"]}
:fn/min	Two or more timestamps.	Returns the smallest (earliest) of all given timestamps.	{:fn/min [{:fn/timepoint [:time/booking-start]} {:fn/timepoint [:time/booking-display-start]}]}
:fn/plus	A timestamp + 1 or more timespans	Returns the timestamp with all the timespans added to it.	{:fn/plus [{:fn/timepoint [:time/booking-start]} {:fn/period "P1D"}]}
:fn/minus	A timestamp + 1 or more timespans	Returns the timestamp with all the timespans substracted from it.	{fn/minus [{:fn/timepoint [:time/booking-end]} {:fn/period "P2D"}]:}
:fn/ignore-if-past	A timestamp	Returns the given timestamp as is unless it's in the past, in which cases returns nothing. Returning nothing from a time expression cancels scheduling the operation.	{:fn/ignore-if-past [{:fn/timepoint [:time/booking-start]}]}

The time functions can be nested freely.

Period expressions

The function :fn/period accepts an ISO 8601 duration as string. For more about the ISO 8601 duration format see: https://en.wikipedia.org/wiki/ISO_8601#Durations

Timepoints

Timepoint	Arguments	Description	Example
:time/tx-initiated	-	The timestamp for when the transaction was initiated.	{:fn/timepoint [:time/tx-initiated]}
:time/first-entered-state	State name as keyword.	The timestamp when the process entered the given state for the first time. Processes may contain loops so a state can be entered multiple times.	{:fn/timepoint [:time/first-entered-state :state/state-name]}
:time/first-transitioned	Transition name as keyword.	The timestamp when the process executed the given transition successfully for the first time.	{:fn/timepoint [:time/first-transitioned :transition/transition-name]}
:time/booking-start	-	The booking start timestamp.	{:fn/timepoint [:time/booking-start]}
:time/booking-end	-	The booking end timestamp.	{:fn/timepoint [:time/booking-end]}
:time/booking-display-start	-	The booking display start timestamp.	{:fn/timepoint [:time/booking-start]}
:time/booking-display-end	-	The booking display end timestamp.	{:fn/timepoint [:time/booking-end]}

A booking always has start and end times. You may optionally specify display start and display end times via transition parameters. Start and end times are used by all actions that automatically calculate prices based on booking length. The automatic availability management also relies on start and end times. The display versions of the start and end times are just for showing to users in the UI but you can additionally use them in time expressions and transaction email templates. Finally, if display times are not specified via transition params they default to booking start and end times.