URL grammar

Every route serves the SDMX-REST 2.2.2 URL grammar, and the data plane takes no API version.

Why one generation

SDMX-REST 2.2.2 makes the time dimension a key slot. SDMX-REST 1.5 and 2.1 keep time out of the key and filter it with startPeriod and endPeriod, so a 1.5 key has one segment fewer for the same data structure.

The two generations' keys cannot be told apart by looking at them. Code that reads a 1.5 key against the 2.2.2 slot list, and pads it or skips the length check, shifts every value one dimension and returns a well-formed wrong answer. The routes read a key against the slot list data/projection.py:key_dimension_ids returns, and sl.parse_components refuses a key of the wrong length, so a 1.5 key sent to these routes is a 400 that names the dimensions. tests/test_key_slots.py pins the slot order and the refusal.

key_dimension_ids returns dsd.key_slot_ids("3.0") when the registry returns a materialised DataStructure. For a missing or lazy DSD it returns the order of the binding's dimension_column_map, which the producer writes; time is then a key slot only if the producer's map includes it.

Older generations

A consumer that serves SDMX-REST 1.5 runs a forwarder. The forwarder knows which generation its URL belongs to, translates the request, and passes a 2.2.2 request to these routes. The routes never guess a key's generation.

AvailabilityKey keys on the resolved dataflow URN, so a 1.5 path and a 2.2.2 path for the same flow share one precomputed entry, and two flows stay distinct under any forwarder path shape.

Backported spellings

Two 1.5 conveniences are accepted on the 2.2.2 routes because they cannot be misread: the all key, and startPeriod and endPeriod. A further spelling is added on the same terms: it must have one reading under both grammars. The availability path without a componentID is a forwarder's to route to all; routes/availability.py registers only the six-segment path (GH-76).