# Measurement Data Types

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The `data` map of a [MeasurementComponent](rhopoint-elements-hub-rae-file-format-measurementcomponent.md) is **polymorphic**: depending on the component type it holds a single value, an embedded file, or a file reference. All variants share a common set of base keys.

### Base keys (all data records)

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| — | `class` | — | string | Type discriminator, see below. Only present in the binary (CBOR) encoding. |
| ClassType | `classType` | `class` | string | Logical type of the record: `"SingleMeasurement"` or `"FileReference"`. |
| Version | `version` | `ver` | integer | Schema version of the data record. Currently `1`. |
| ValueType | `valueType` | `valueType` | string | .NET type name of the value, e.g. `"System.Double"`, `"System.Int32"`. |
| SerializedValue | `serializedValue` | `value` | string | The value serialized as a JSON string, e.g. `"42.42"`. |
| Value | `value` | — | any | The value encoded natively (number, string, map, …). Only present in the binary (CBOR) encoding. |

> [!warning]
> The key `class` means different things in the two encodings, and so does `value`:
> - In the **binary (CBOR)** encoding, `class` is the type discriminator (the internal record name, e.g. `"SingleMeasurementDataGenericDto"`, `"FileReferenceDataGenericDto"` or `"FileBinaryDataGenericDto"`) and the logical type lives in `classType`. The native value lives in `value`, and the JSON-serialized copy in `serializedValue`.
> - In the **[JSON Variant](rhopoint-elements-hub-rae-file-format-json-variant.md)**, `class` holds the logical type (`"SingleMeasurement"` / `"FileReference"`) and `value` holds the JSON-serialized value string. There is no separate discriminator or native value.

When reading a binary RAE file, use `class` to select the concrete record type. To read the value itself you can usually use the native `value` directly; the reference implementation reconstructs it from `serializedValue` + `valueType`.

### SingleMeasurementData

Used with `single` components. It adds no keys beyond the base keys — the measurement value lives in `value` / `serializedValue`. The value is typically a number, but any JSON-serializable type is allowed (`valueType` tells you what it is).

Example (CBOR diagnostic notation):

```
{
  "class": "SingleMeasurementDataGenericDto",
  "classType": "SingleMeasurement",
  "version": 1,
  "valueType": "System.Double",
  "serializedValue": "87.3",
  "value": 87.3
}
```

### FileReferenceData

Used with `fileReference` components. It describes a file without embedding its content:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| FileIdentifier | `fileIdentifier` | `fileId` | string | Identifier of the file. |
| Filename | `filename` | `name` | string | Original file name. |
| MimeType | `mimeType` | `type` | string | MIME type of the file content (e.g. `"image/png"`, `"image/x-raw"`). |
| HashData | `hashData` | `hash` | map | Hash of the file content, see below. |
| Metadata | `metadata` | `meta` | map | File metadata, see below. |

The **HashData** map:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| Algorithm | `algorithm` | `alg` | string (enum) | Hash algorithm. Currently `"sha256"`. |
| Hash | `hash` | `hash` | string | The hash value. |

The **FileMetadata** map:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| Author | `author` | `author` | string | Author of the file. |
| Created | `created` | `created` | string (ISO 8601) | Creation time of the file. |

### FileBinaryData

Used with `file` components. It extends `FileReferenceData` by embedding the file content:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| BinaryData | `binaryData` | `bin` | byte string | The raw file content. In the binary encoding this is a CBOR byte string; in the [JSON Variant](rhopoint-elements-hub-rae-file-format-json-variant.md) it is Base64-encoded. |

Device images returned by Elements Hub use this record — see [Measurement Image Formats](rhopoint-elements-hub-measurement-image-formats.md) for the image encodings and how to decode the `image/x-raw` payload.

Example (CBOR diagnostic notation, binary data shortened):

```
{
  "class": "FileBinaryDataGenericDto",
  "classType": "FileReference",
  "version": 1,
  "valueType": null,
  "serializedValue": null,
  "value": null,
  "fileIdentifier": "surfaceImage",
  "filename": "surfaceImage.png",
  "mimeType": "image/png",
  "hashData": null,
  "metadata": null,
  "binaryData": h'89504E470D0A1A0A...'
}
```