ADR-0015 — Generic events, occurrences, and a year set by hand

Status: Accepted · Date: 2026-11-06 · Concerns the ontology, the edge and the cloud

Context

Every event needed a start date and one type. A family that wanted one "Anniversaire" for all birthdays had to give it a range such as 2000–2026, and a separate "Anniversaire 2017" for every year it cared about. The year of a photo was taken only from the file, which is wrong for scans and copies.

Decision

A generic event has no date. schema:startDate becomes optional (at most one). "Anniversaire", "Christmas", "Holidays at Lakeside" are events with a type, attendees and a place, but no date. A photo tagged to one keeps its own year.

The year is a separate facet. The Library already filters by year, from each photo's effective date, and by event; the two combine. "Anniversaire" + 2017 needs no event of its own. The specific occasion, where it matters, is usually already an album (the folder it came from).

An occurrence, when one year needs its own facts. "Anniversaire 2017", with its own date, attendees or place, is schema:superEvent of the generic event. A photo of the occurrence counts for the generic event too: the Library's effective events of an item are its own events, then their generic events (eventsWithGeneric, cycles stopped). The event filter lists generic events first, each with its occurrences under it (eventTree).

A year set by hand. mt:year (xsd:gYear, at most one) on a photo or film. It wins over the file's date in the Library (dateSource: "year"); month and day are not guessed, so the effective date is the 1st of January. Clearing it returns to the file's date. Set in the tagging wizard for the chosen photos, and on one photo in the viewer.

More generic event types, as data in mediathek-concepts.ttl (EN, DE, FR): Anniversary (jubilee), First communion, Confirmation, Housewarming, Carnival, Halloween, Day trip, Weekend trip; and three new top concepts, Life event (Birth, Moving house, Retirement, Funeral), Work event (Company party) and Everyday.

Consequences

• Deploy the cloud first. An older cloud refuses a dateless event or an mt:year from a newer edge with a 400 at sync.
• An event without a date sorts after the dated ones; nothing derives a date from it, so an undated photo of a generic event stays undated (filter "without a date").
• An occurrence's attendees count for photos of the occurrence; a generic event's attendees count for every photo under it. Put people on the occurrence when they were there only that year.
• The edge reads mt:year and schema:superEvent from the A-Box like any other statement; both are single-valued in sync (sync.SINGLE).