# Unit processes, LCI and LCIA

## Definitions

The [glossary](/en/data-reference/glossary#standard-terms) provides definitions and standard references for unit processes,
life cycle inventory analysis, life cycle impact assessment and characterization factors.

The following levels apply when reading this site's data:

| Data level              | Use                                                                                                                                   |
| ----------------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| Unit process (UPR)      | Read the process's own inputs and outputs. Cumulative results cannot be used to reconstruct its direct exchanges.                     |
| Inventory results (LCI) | Read quantified inputs and outputs within the product system boundary. Inventory results are distinct from the LCI analysis phase.    |
| Cumulative LCI          | Read elementary flows aggregated across upstream processes. This is an inventory result, not another name for the LCI analysis phase. |
| LCIA results            | Read results for a specific impact assessment method, impact category and category indicator.                                         |

## Result fields

See [reference quantities and units](/en/data-reference/reference-quantities-and-units#definitions) for the distinction between reference
product quantities, elementary flow quantities and category indicator units. Specific request and response fields are
documented under [API result fields](/en/data-access/query-api#result-fields).

Distinguish [Method UUID](/en/resources/file-definitions#lcia-methods) from [Method ID](/en/resources/file-definitions#impact-categories). A method
identifier is not interchangeable with a composite identifier for a particular category indicator.

## Endpoints

See [API endpoints](/en/data-access/query-api#endpoints) for cumulative LCI, LCIA results and impact assessment method
catalogs. Unit process direct exchanges are outside the query API's [response scope](/en/data-access/query-api#response).