> For the complete documentation index, see [llms.txt](https://docs.diracinc.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.diracinc.com/how-to-be-successful-in-buildos/concepts/model-based-definition.md).

# Model-Based Definition

This will cover what model-based definition is and how it works in BuildOS.

## What is model-based definition?

Model-based definition (MBD) allows you to link CAD part geometry to structured metadata such as part numbers, names, revisions, materials, and manufacturers. This metadata is automatically extracted from your CAD models and can be mapped from multiple sources.

Instead of maintaining separate spreadsheets or documents, the information lives alongside the CAD data and flows into your work instructions automatically.

## Available metadata fields

BuildOS supports the following metadata fields:

* **Item Number** — Part or component number
* **Item Name** — Descriptive name of the part
* **Revision** — Version or revision identifier
* **Material** — Material specification
* **Bought/Made (Manufacturer)** — Whether the part is purchased or fabricated, and the manufacturer

## Metadata sources

Each metadata field can be mapped to one or more data sources with priority ordering. When multiple sources are configured, BuildOS uses the highest-priority source that has data available.

You can map up to 5 sources per field. Sources are checked in priority order from left to right, and the first source with data is used.

Metadata associations are configured at the team level, so all team members share the same mappings.