Schedules

A Schedule is a representation of a recurrence rule, compatible with the iCalendar specification, designed to be extrapolated by the data user into individual occurrences.
A PartialSchedule, by contrast, must not be extrapolated by the data user, and is for information only.
Outputting a Schedule to a feed
A Schedule must be included in the SessionSeries feed for systems that display occurrences of a sessions directly from a recurrence rule (as opposed to first materialising them into a database).
Complementary ScheduledSessions
It is recommended that a ScheduledSession feed be published alongside any SessionSeries feed that contains Schedules, and that this ScheduledSession feed also includes remainingAttendeeCapacity. If implementing the Open Booking API, such a complementary feed is required.
When ScheduledSessions are included in a feed or subEvent, they must not include all occurrences that are generated from the recurrence rule, and instead must only include those events that either:
1.Have bookings associated (i.e. where remainingAttendeeCapacity < maximumAttendeeCapacity)
2.Are an exception to the recurrence rule defined in the Schedule.
3.Have any other properties that differ from those defined in SessionSeries.
Such events would need to have been materialised in a database within the booking system already, so under no circumstances should new occurrence records be generated for the sole purpose of outputting them to an OpenActive ScheduledSessions feed.
This constraint is necessary to prevent recurrence rules from creating a high volume of redundant data in its ScheduledSession feed. For example: if a SessionSeries has a recurrence rule for a weekly event with an endDate in 2050, only the ScheduledSessions that have been booked at least once or have been manually edited would appear in the ScheduledSession feed.
Using templates
When such ScheduledSessions are included, the Schedule must also include an idTemplate, such as the below, which matches the pattern of the @id of the ScheduledSessions (noting the startDate placeholder must use a string format of YYYY-MM-DDThh:mm:ssZ (e.g. 1997-07-16T19:20:00Z):
"idTemplate": "https://api.example.org/session-series/123/{startDate}"
A urlTemplate may also be included in the Schedule using the same startDate placeholder.
Note that if a single ScheduledSession that was previously generated by a Schedule is rescheduled to a different start time, its original @id must be retained (which contains the original start time), to ensure that it still hides the same generated occurrence (see below), and to ensure that Change of Logistics Notifications are still triggered.
Also note that if a Schedule is updated, it must include exceptDates for any overlaps with any  explicitly defined occurrences created from previous Schedules, as they might have been rescheduled based on a previous @id.
Processing a Schedule found in a feed
In order to process a Schedule together with complimentary ScheduledSessions, the data user must do the following:
1.Generate all occurrences from a Schedule in the future, taking into account the exceptDate property.
Take the scheduledEventType, property and use it for the @type property of each occurrence.
Use an RRULE library to calculate the startDate of the occurrences based on the contents of the Schedule. DTSTART must be determined by using the startDate, startTime, and scheduleTimezone of the Schedule together, for example:
{
  "@type": "Schedule",
  "startDate": "1997-09-02",
  "startTime": "09:00",
  "endTime": "10:00",
  "duration": "PT1H",
  "scheduleTimezone": "America/New_York",
  "repeatFrequency": "P1D",
  "repeatCount": 10
}
DTSTART;TZID=America/New_York:19970902T090000
RRULE:FREQ=DAILY;COUNT=10
For the avoidance of doubt: the startDate and startTime of the Schedule are in "local time" based on the scheduleTimezone.
Use the duration of the Schedule to calculate the endDate of each occurrence.
Render the calculated startDate and endDate for each occurrence to UTC using a string format of YYYY-MM-DDThh:mm:ssZ (e.g. 1997-07-16T19:20:00Z) for placeholder replacement.
Take the idTemplate property (if provided) and substitute the startDate placeholder with the calculated string value of startDate (and do the same with endDate). Use the resulting string as the value of the @id property for the occurrence.
Take the urlTemplate property (if provided) and substitute the startDate placeholder with the calculated string value of startDate (and do the same with endDate). Use the resulting string as the value of the url property for the occurrence.
2.To account for any changes in the Schedule since the last time it was updated, store the generated occurrences as follows:
1.Upsert all generated occurrences, marking them with the modified RPDE timestamp associated with the Schedule. Ensure that any explicitly defined occurrences that may have been generated from a previous run of Step 3 (below) are not overwritten by this step.
2.Delete all generated occurrences that do not have an older modified RPDE timestamp associated with the Schedule.
3.Ensure the generated occurrences are hidden by any matching explicitly defined occurrences (e.g.ScheduledSessions found in a subEvent or ScheduledSession feed), using the explicitly defined occurrence in its entirety based on its @id.
Example
Extract from SessionSeries feed:
{
  "@type": "SessionSeries",
  ...
  "eventSchedule": [
    {
      "@type": "Schedule",
      "repeatFrequency": "P1W",
      "startDate": "2018-03-01",
      "endDate": "2018-03-29",
      "startTime": "08:30",
      "endTime": "09:30",
      "byDay": [
        "https://schema.org/Thursday"
      ],
      "duration": "PT1H",
      "exceptDate": [
        "2018-03-15T08:30:00Z",
      ],
      "scheduleTimezone": "Europe/London",
      "scheduledEventType": "ScheduledSession",
      "idTemplate": "https://api.example.org/session-series/1402CBP20150217/{startDate}",
      "urlTemplate": "https://example.org/session-series/1402CBP20150217/{startDate}"
    }
  ]
}
Extract from ScheduledSession feed:
{
  "state": "updated",
  "kind": "ScheduledSession",
  "id": "C5EE1E55-2DE6-44F7-A865-42F268A82C63",
  "modified": 1521565719,
  "data": {
    "@context": "https://openactive.io/",
    "@type": "ScheduledSession",
    "@id": "https://api.example.org/session-series/1402CBP20150217/2018-03-15T10:30:00Z",
    "identifier": "C5EE1E55-2DE6-44F7-A865-42F268A82C63",
    "superEvent": "https://example.com/api/session-series/1402CBP20150217",
    "startDate": "2018-03-15T10:30:00Z",
    "endDate": "2018-03-15T11:30:00Z",
    "duration": "PT1H",
    "eventStatus": "https://schema.org/EventScheduled",
    "maximumAttendeeCapacity": 10,
    "remainingAttendeeCapacity": 10,
    "url": "https://example.org/session-series/1402CBP20150217/2018-03-15T10:30:00Z"
  }
},
{
  "state": "updated",
  "kind": "ScheduledSession",
  "id": "C5EE1E55-2DE6-44F7-A865-42F268A82C64",
  "modified": 1521565719,
  "data": {
    "@context": "https://openactive.io/",
    "@type": "ScheduledSession",
    "@id": "https://api.example.org/session-series/1402CBP20150217/2018-03-22T08:30:00Z",
    "identifier": "C5EE1E55-2DE6-44F7-A865-42F268A82C64",
    "superEvent": "https://example.com/api/session-series/1402CBP20150217",
    "startDate": "2018-03-22T08:30:00Z",
    "endDate": "2018-03-22T09:30:00Z",
    "duration": "PT1H",
    "eventStatus": "https://schema.org/EventScheduled",
    "maximumAttendeeCapacity": 10,
    "remainingAttendeeCapacity": 3,
    "url": "https://example.org/session-series/1402CBP20150217/2018-03-22T08:30:00Z"
  }
}
Illustration of resulting opportunities presented to the end user:
Last modified 2yr ago
Schedules

Outputting a `Schedule` to a feed

Complementary `ScheduledSession`s

Using templates

Processing a `Schedule` found in a feed

Example
