# Validated against FROST-Server Run 2026-10-07 against `fraunhoferiosb/frost-server:latest` with `postgis/postgis:16-3.4`. Companion to [sdk/sensorthings.py](../../sdk/sensorthings.py). The completeness matrix in [VIRTUAL_FARM.md](../VIRTUAL_FARM.md) had this row as a claim: a serializer exists, but "existing tools work on day one" is untested until a real implementation has accepted its documents. FROST-Server is the right oracle — it is the most widely deployed STA server, from the same institute as the 2.0 editor, so what it accepts is what the ecosystem accepts in practice. ## Method Stand FROST up, deep-insert a Thing carrying a Datastream, ObservedProperty, Sensor, Observation and FeatureOfInterest shaped exactly as the adapter emits them, read them back, and diff key-by-key against the adapter's own output for the same logical entity. FROST assigns its own ids and selfLinks, so those are excluded from the diff; everything else is compared. ## What held **The deep insert returned `201 Created`.** The document shapes are valid 1.1, not merely plausible. **`resultQuality` survived as a list of arbitrary objects**, nested `evidence` included. §3.3's flag *set* therefore maps natively onto 1.1's `DQ_Element` with multiplicity zero-to-many, exactly as [sensorthings-2.0.md](sensorthings-2.0.md) predicted — and it is the capability the 2.0 draft drops, which is the concrete argument for raising Q18. **`parameters/fieldmesh` survived intact.** The namespacing decision — layer-zero fields nested rather than posing as 1.1's "environmental conditions during measurement" — costs nothing in the reference implementation. **`resultTime: null` on an Observation was accepted** and returned as null, so the honest encoding of "layer zero does not record when the result was generated" is legal rather than a workaround. `phenomenonTime` as an instant with `Z`, `unitOfMeasurement` as `{name, symbol, definition}` with a UCUM definition, and a Datastream `properties` object carrying `kind`, `derived_from`, `expected_interval_s`, `thresholds` and `health` were all accepted and returned verbatim. After the two fixes below, the Datastream and Observation documents are at **full key parity** with FROST's. ## What the oracle caught **`resultTime` on a Datastream.** 1.1 Table 10 makes it zero-to-one. The adapter emitted it as `null`; FROST omits it. A bare null for an optional field layer zero has nothing to say about is noise, so the adapter now omits it. Observation's `resultTime` is "One (mandatory)" and nullable, so that one stays null — the two fields look alike and are not. ## A defensible divergence, now a parameter **`@iot.count` on an entity set.** FROST omits it unless `$count=true` is asked for. 1.1's own Example 11 shows it in the response to a plain entity-set request with no query options. Both read the spec reasonably, so this is not a bug in either: `collection(..., count=...)` makes it switchable, defaults to including it per Example 11, and an HTTP layer passes `$count` through. ## A finding about ids, not a defect FROST with default configuration **rejects a client-supplied string id**: ``` 400 Cannot deserialize value of type java.lang.Long from String "a-uuid-like-string" ``` Its ids are `Long`. §1 requires UUIDv7, and 1.1 does not constrain the id type, so the adapter is within the standard; FROST is configurable in this respect (`persistence_idGenerationMode` and friends). The practical consequence is worth stating: **FROST cannot be used to round-trip our ids without reconfiguration**, so it serves as an oracle for *document shape*, not as a store for layer-zero data. Nothing in the spec needs to change. ## Since done What was outstanding here — a GIS client reading these documents, which needed the HTTP layer with `$filter`, `$expand`, `$top` and paging — has been done: QGIS 3.44 and Fraunhofer's client read the service and found five defects no internal test could reach ([qgis-validation.md](qgis-validation.md)). ## Three more questions put to the oracle, 2026-10-07 Asked while validating the HTTP layer in [server/](../../server/) against two real clients — see [qgis-validation.md](qgis-validation.md) for the full account. | Question | FROST's answer | What it settled | | --- | --- | --- | | Does `$top=2` suppress `@iot.nextLink`? | **No.** Two rows *plus* `?$top=2&$skip=2`. With `$count=true`, the count is the unfiltered total and the nextLink carries `$count` forward | Our paging matches the reference implementation exactly. A change to suppress the nextLink on an explicit `$top` was drafted on a reading of OData and **not made**, because the oracle outranks the reading | | Is `unitOfMeasurement` required when `observationType` is `OM_CountObservation`? | **Yes.** With a unit: 201. Without: **400** | Our count-with-a-unit document was a semantic defect, not a protocol violation — and a raw datastream declaring a null unit could not be mirrored into FROST, which constrains [Q21](../spec/open-questions.md) | | Can a Thing be deep-inserted with Datastreams and Observations and no Location? | **No.** `No FeatureOfInterest provided, and none can be generated.` | FROST generates features of interest from Thing Locations; layer zero derives them from the datastream's declared feature (§3.1). A different and deliberate choice, but anyone mirroring into FROST will meet it | ## Reproducing ```sh docker network create frostnet docker run -d --name frost-db --network frostnet \ -e POSTGRES_DB=sensorthings -e POSTGRES_USER=sensorthings \ -e POSTGRES_PASSWORD=ChangeMe postgis/postgis:16-3.4 docker run -d --name frost --network frostnet -p 8080:8080 \ -e persistence_db_driver=org.postgresql.Driver \ -e persistence_db_url=jdbc:postgresql://frost-db:5432/sensorthings \ -e persistence_db_username=sensorthings -e persistence_db_password=ChangeMe \ -e persistence_autoUpdateDatabase=true \ -e serviceRootUrl=http://localhost:8080/FROST-Server \ fraunhoferiosb/frost-server:latest curl -s http://localhost:8080/FROST-Server/v1.1/ ``` The findings are pinned as tests in `sdk/test_sensorthings.py` (`TestValidatedAgainstFrost`), so they survive without the container.