The Unified Astronomy Thesaurus is an open reference vocabulary for the Astronomy community at large.  In response to the needs of our community and as our knowledge of the field evolves, the UAT will undergo regular revisions and updates.  This short document details our plan for managing versioned releases so as to minimize disruptions while providing needed updates to the users of the Thesaurus.  For more information about how changes are evaluated, read our Curation Process.

Release Cycle

To ensure that the UAT continues to represent the latest research in our fields, the Thesaurus will be reviewed for potential updates  at least once a year. This schedule will allow us to analyze the literature to detect new concepts and rethink the UAT’s existing structure. Community feedback and use cases may dictate a more frequent update cycle (e.g. quarterly updates).  For more details about this schedule see the Release Cycle document.


The UAT is implemented by a variety of information providers and in multiple contexts.  The UAT follows specific versioning guidelines to help all users understand the scope of change from one release to the next. Versioning also helps users determine whether or not implementing UAT updates may require changes in their particular applications.

The versioning model we use was inspired by the Semantic Versioning pattern used for software (  As the UAT is essentially a data project, and not a software package, many of the core features of Semantic Versioning surrounding backwards compatibility and overall functionality do not apply.  However, we’ve decided to utilize the idea of SemVer’s prescribed release naming pattern to denote the significance of changes from one version to the next, namely: MAJOR.MINOR.PATCH, where MAJOR, MINOR, and PATCH are digits.

This naming pattern can help give users and developers a sense of how significant the changes are between versions, which can guide adoption and use.  Taking into consideration the impact that various suggestions have on how the Unified Astronomy Thesaurus describes our understanding of astronomy helps to guide the evaluation and vetting process.

In the case of the UAT, the following guidelines will govern changes in the three categories:

MAJOR changes to the UAT are reflective of notable scientific developments and increases in the representation of major concepts.  Examples of MAJOR changes from previous release notes include:

  • Added 3 new branches:
    • Astrostatistics
    • Laboratory astrophysics
    • Astronomy software
  • Major revisions of various branches:
    • Stellar astronomy
    • Solar physics
    • Computational astronomy

MINOR changes to the UAT increase granularity and improves representation of established concepts.  Examples of MINOR changes from previous release notes include:

  • Minor revisions of two branches:
    • Gravitational lensing
    • Comets
  • 16 new concepts were added to the UAT.
  • Deprecated 7 concepts.

PATCH changes to the UAT are unanticipated minor adjustments that don’t impact the hierarchy.  Examples of PATCH changes from previous release notes include:

  • The preferred label of 88 concepts were updated to add context, clarity, and consistency.
  • Added or updated AltLabels for 51 concepts, removed AltLabels for 4 concepts.
  • Added 8 definitions, 15 scope notes, and 1 example.