> For the complete documentation index, see [llms.txt](https://docs.geosamples.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.geosamples.org/metadata-schema/readme.md).

# Overview & data model

What SESAR stores about a sample, what is required, and how fields map from legacy and external schemas.

This section covers SESAR sample metadata: requirements, the database schema, legacy migrations, and external crosswalks. Controlled term lists are in **Vocabularies**; programmatic create/update is in **API**.

| If you want to…                                                       | Start here                                                                                                               |
| --------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| View a "Quick Guide" to SESAR's database schema/fields                | [SESAR schema quick guide](/metadata-schema/schema-quick-guide.md)                                                       |
| Understand what fields are required vs optional for all SESAR records | [Field requirements](/metadata-schema/field-requirements.md)                                                             |
| Closely inspect SESAR's data structures                               | [Detailed database schema](/metadata-schema/database-schema.md)                                                          |
| Understand how SESAR 1.0 fields to the new schema                     | [Field crosswalk (old → new)](/metadata-schema/migration-from-the-legacy-schema/field-crosswalk-old-greater-than-new.md) |
| Understand how controlled vocabularies were renamed or changed        | [Renamed vocabularies](/metadata-schema/migration-from-the-legacy-schema/renamed-vocabularies.md)                        |
| Map old sample types to object type                                   | [Sample type to object type](/metadata-schema/migration-from-the-legacy-schema/sample-type-to-object-type.md)            |
| Map old classification to material type                               | [Classification to material type](/metadata-schema/migration-from-the-legacy-schema/classification-to-material-type.md)  |
| See how SESAR metadata is mapped to DataCite records                  | [DataCite](/metadata-schema/crosswalks/datacite.md) crosswalk                                                            |


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