Cognite Data Fusion Unit Catalog

This repository stores a comprehensive unit catalog for Cognite Data Fusion (CDF) with a focus on standardization, comprehensiveness, and consistency. The catalog is maintained in two primary JSON files:

1. units.json: Contains a list of units with their metadata.
2. unitSystems.json: Contains various unit systems and their quantities.

Structure

units.json

Each item in the units.json has the following structure:

{
    "externalId": "string",
    "name": "string",
    "longName": "string",
    "symbol": "string",
    "aliasNames": ["string", ...],
    "quantity": "string",
    "conversion": {
        "multiplier": "float",
        "offset": "float"
    },
    "source": "string",
    "sourceReference": "URL"
}

• externalId: The external identifier for the unit. Its structure follows the pattern {quantity}:{unit} (e.g., temperature:deg_c), adhering to the snake_case convention.
• name: The primary name of the unit (e.g., DEG_C).
• longName: A descriptive name for the unit (e.g., degree Celsius).
• symbol: The symbol for the unit (e.g., °C).
• aliasNames: An array of possible aliases for the unit.
• quantity: Specifies the physical quantity the unit measures (e.g., Temperature).
• conversion: An object containing multiplier and offset values for converting between units.
• source: The primary source of the unit (e.g., qudt.org).
• sourceReference: A URL reference to the unit definition on an external source, if available.

unitSystems.json

Each item in the unitSystems.json has the following structure:

{
    "name": "string",
    "quantities": [
        {
            "name": "string",
            "unitExternalId": "string"
        },
        ...
    ]
}

• name: The name of the unit system (e.g., default, SI).
• quantities: An array containing the physical quantities and their associated units in the system.

Validations and Tests

To ensure the integrity of the catalog, the following tests are conducted:

1. Syntax Check: Every unit item in units.json must have the specified keys.
2. Unique IDs: All unit externalIds in units.json must be unique.
3. Reference Validation: There should be no references to non-existent unit externalIds in unitSystems.json.
4. Default Quantities: All quantities must be present in the unitSystems.json for the default quantity.
5. Consistent References: All quantity references in unitSystems.json must exist in units.json.
6. Unique Quantity-Alias Pairs: All pairs of (alias and quantity) must be unique across all units, for all aliases in aliasNames.
7. Unique Unit Aliases: Each unit's aliasNames array must contain only unique values, with no duplicate entries allowed.
8. ExternalId Format: All unit externalIds must follow the pattern {quantity}:{unit}, where both quantity and unit are in snake_case.

Attribution

Some of the units are sourced from QUDT.org, which is licensed under the Creative Commons Attribution 4.0 International License. These are marked with the qudt.org source.

Code ownership

Copyright 2023 Cognite AS

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

This license applies to any code/data file in this repository, unless otherwise noted.

Contribution

To maintain the consistency and quality of the unit catalog, please ensure any contributions adhere to the established structure and guidelines. Before submitting any additions or modifications, ensure that all tests pass.