Schema Metadata: Semantic Column Types (Built-In Taxonomy)

Issue 77 Edition 2026-03-18 3 min read

Not accepted General

Sources: 1 • Confidence: Medium • Updated: 2026-04-12 10:16

Key takeaways

Datasette supports assigning semantic column types to columns.
Datasette version 1.0a26 has been released.
Datasette plugins can register additional semantic column types via a register_column_types() plugin hook.
Datasette includes built-in semantic column types: url, email, and json.

Datasette plugins can register additional semantic column types via a register_column_types() plugin hook.

What concrete behaviors in Datasette change when a column is assigned a semantic type (e.g., display formatting, linking, validation, API output, search/filter behavior)?
How are semantic column types stored and represented (e.g., configuration files, database metadata tables, plugin-provided metadata), and how are they surfaced in APIs?
What is the full set of built-in semantic column types beyond url, email, and json (if any), and what are their semantics?
What are the compatibility expectations for the register_column_types() hook across future 1.0 alpha releases (e.g., signature stability, namespacing, conflict resolution between plugins)?
Are existing plugins already adopting register_column_types(), and is there emerging convergence on shared semantic types across plugins?

Datasette is moving toward higher level schema metadata, which could improve usability and interoperability for users and developers beyond raw database types.
Introducing register_column_types suggests a growing plugin API surface and a potential ecosystem push toward shared semantic conventions across plugins.
The 1.0a26 release milestone indicates accelerating pre 1.0 feature delivery, potentially increasing near term testing and adoption by plugin authors.

Documentation or release notes clarifying concrete behaviors tied to semantic types, such as display formatting, linking, or API representation.
Evidence that multiple plugins adopt register_column_types and converge on common semantic type names and semantics.
Stated compatibility expectations for the register_column_types hook across subsequent 1.0 alpha releases, including conflict handling between plugins.

Semantic types remain mostly cosmetic with minimal behavior changes, limiting practical value for users and developers.
Frequent breaking changes to the register_column_types hook across alpha releases, discouraging plugin adoption.
Fragmentation where plugins register overlapping or conflicting semantic types without a path to standardization.