RRULEa

RRULEa is a hypothetical extension of the iCalendar RRULE recurrence rule intended to express adaptive or context-aware recurrences. It appears in theoretical discussions and experimental software as a concept for scheduling events whose occurrence depends on external factors rather than fixed cadence alone.

Like RRULE, RRULEa describes patterns through components such as FREQ, INTERVAL, COUNT, and UNTIL. A key addition is the A component (adaptive factor), which encodes a rule or function used to modify the effective schedule in response to conditions such as holidays, daylight changes, or user availability.

Syntax and semantics are not standardized. In proposed designs, RRULEa strings resemble RRULE strings with the same core fields plus an optional A field, for example RRULEa:FREQ=WEEKLY; INTERVAL=1; BYDAY=MO; A=holiday_adjustment. Implementations vary and most calendar tools do not recognize RRULEa without dedicated parsers.

Usage scenarios include adaptive meetings that avoid public holidays, or event series that pause during certain seasons. The adaptive logic is typically evaluated ahead of time or at recurrence generation, and may be constrained to remain within an overall UNTIL or COUNT bound.

Status and reception: RRULEa remains a niche concept, not part of any formal standard. It is primarily discussed within research contexts and example libraries to illustrate how recurrence could be made context-aware; widespread interoperability has not been established. See also RRULE, iCalendar, and recurrence rules.