> For the complete documentation index, see [llms.txt](https://kb.bravegen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kb.bravegen.com/carbon/core-concepts/activity-sources.md).

# Activity Sources

How activity is handled in BraveGen Carbon, and grouped for emissions reporting

Activity Sources are 'channels' of data within BraveGen, allowing you to track the values of an activity over time.

#### What Defines a Source?

A source is comprised of a 'checksum' of multiple properties defined by a [data map](/carbon/core-concepts/data-collection/processes/file-upload/data-maps.md), or as the result of ingesting data. If any of these values differs during ingestion, then the system will flag a new source during the [task review](/carbon/core-concepts/data-collection/tasks/task-reviews.md#what-determines-a-new-source) step.

A source tracks the following channels of data:

* Activity
* Date From
* Date To (optional)
* Cost (optional)
* Commentary (optional)

For spend-based activities, the activity and the cost channel values are the same.

### Source Properties

The following properties can be set for every source. [Refrigerant Sources](/carbon/core-concepts/activity-sources/refrigerant-sources.md) have additional properties.

* Source Name
* Supplier
* Goods & Service
* Identifiers
* Source Type
* Description
* Tags
* Inventory Rule
* Entity
* Unit of Measure
* Aggregation (see methodology below)
* Cost Currency
* Region
* Mapping Aliases (shown when multiple sources are merged together)
* Contacts

### Aggregation Methodology

All sources have an *aggregation* property. This defines how data in the source is reported if there are multiple data entries during the reporting period. A source can only have a single aggregation method - this is updated from the source details view.

<table><thead><tr><th width="141.91015625">Methodology</th><th>Behaviour</th><th>Examples</th></tr></thead><tbody><tr><td>SUM</td><td>Data entries are summed across the reporting period. (Default)</td><td>Eg. Spend or volume, where totals are used</td></tr><tr><td>LATEST</td><td>The latest entry value is used from the reporting (or previous) period.</td><td>Eg. Ratings, FTE, Floor Area</td></tr></tbody></table>

{% hint style="info" %}
Note: BraveGen will apply the Aggregation Methodology when rolling up data across entities.&#x20;
{% endhint %}

Monthly is our lowest reporting granularity, so Source Data is kept at monthly grain. Transactional records within a month are grouped into a single monthly row. This grouping has nothing to do with the Aggregation Method, it is a fixed data reduction rule.&#x20;

As a result a source with LATEST method holds at most one value per month. If a new value arrives for a month that already has one, it replaces the old value, it is never added to it.

Original CSV files are kept unchanged, with their checksums, as the audit record. Any monthly row can be rebuilt from the transposed files if it is ever questioned.