# MeasurementComponent

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A `MeasurementComponent` is a node in the measurement tree. A measurement is usually a **composite** root component that contains one child component per metric or image; child components can themselves contain further components, so arbitrary hierarchies are possible.

```
Measurement                (composite)
├── Gloss 60°              (single, data = 87.3)
├── DOI                    (single, data = 92.1)
└── ledShadeImages         (array)
    ├── ledShadeImages_0   (file, data = binary image)
    ├── ledShadeImages_1   (file, data = binary image)
    └── ...
```

### Properties

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| Identifier | `identifier` | `id` | string | Database identifier. May be `null`; importers typically discard it and assign a new one. |
| Version | `version` | `ver` | integer | Schema version of the record. Currently `2`. |
| SourceIdentifier | `sourceIdentifier` | `srcId` | string | Identifier assigned by the system that produced the measurement. |
| Type | `type` | `type` | string (enum) | **Required.** The component type, see below. |
| Name | `name` | `name` | string | Name of the component (e.g. the metric name). |
| Timestamp | `timestamp` | `time` | string (ISO 8601) | Time the component was stored. |
| SourceTimestamp | `sourceTimestamp` | `srcTime` | string (ISO 8601) | Time the component was recorded on the source device. |
| Data | `data` | `data` | map | The measurement value or file, see [Measurement Data Types](rhopoint-elements-hub-rae-file-format-measurement-data-types.md). `null` for pure grouping nodes. |
| Metadata | `metadata` | `meta` | map | Additional metadata about the value, see below. |
| Source | `source` | `src` | map | Information about where the measurement was taken, see below. |
| Components | `components` | `comp` | array of maps | Child components (nested `MeasurementComponent` records). |
| SourceSignature | `sourceSignature` | `srcSig` | string | Signature created by the source device (data authenticity). |
| Signature | `signature` | `sig` | string | Signature of the record. |

### Component types

The `type` value is one of the `MeasurementTypes` enum members (written in lowerCamelCase):

| Value | Meaning |
|---|---|
| `single` | A single value; `data` holds the value. |
| `composite` | A grouping node; the children live in `components`. |
| `continuous` | A continuously recorded series of values. |
| `graph` | Graph/curve data. |
| `file` | A file embedded in the component; `data` is a `FileBinaryData` record. |
| `fileReference` | A reference to a file stored elsewhere; `data` is a `FileReferenceData` record. |
| `array` | An ordered collection of components of the same kind (e.g. an image stack). |

### Metadata

The optional `metadata` map describes the value in `data`:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| Unit | `unit` | `unit` | string | Unit of the value (e.g. `"GU"`). |
| Accuracy | `accuracy` | `accuracy` | string | Accuracy of the value. |
| Environment | `environment` | `env` | map | A nested `MeasurementComponent` describing environmental conditions (e.g. temperature) at the time of measurement. |

### Source

The optional `source` map describes where the measurement was taken:

| Property | CBOR key | JSON key | Type | Description |
|---|---|---|---|---|
| DeviceIdentifier | `deviceIdentifier` | `deviceId` | string | Identifier (e.g. serial number) of the measuring device. |
| LocationName | `locationName` | `loc` | string | Human-readable location name. |
| Latitude | `latitude` | `lat` | string | Geographic latitude. |
| Longitude | `longitude` | `lon` | string | Geographic longitude. |

### Declaration

```csharp
public record MeasurementComponent : Identifiable
{
    public required MeasurementTypes Type { get; set; }
    public string? Name { get; set; }
    public DateTimeOffset? Timestamp { get; set; }
    public DateTimeOffset? SourceTimestamp { get; set; }
    public IMeasurementData? Data { get; set; }
    public IMetadata<MeasurementComponent>? Metadata { get; set; }
    public IMeasurementSource? Source { get; set; }
    public List<MeasurementComponent>? Components { get; set; }
    public string? SourceSignature { get; set; }
    public string? Signature { get; set; }
}

public enum MeasurementTypes
{
    Single,
    Composite,
    Continuous,
    Graph,
    File,
    FileReference,
    Array
}
```