# The Unity units library

This is the unity library, which is able to parse scientific unit specifications using a variety of syntaxes.

This is version 1.1, 2023 October 22

Home page: https://purl.org/nxg/dist/unity

Released versions:

Version | Date | Code DOI | Packages
--- | --- | --- | ---
latest |  | 10.5281/zenodo.6949817 | list
1.0 | 2014 May 13 | 10.5281/zenodo.6949818 | package
1.1-b1 | 2022 April 10 |  | package

The library is released under the terms of the 2-clause BSD licence.

The four syntaxes which the library (and VOUnits specification) refers to are:

- the FITS specifications, section 4.3 (see v3.0 (doi:10.1051/0004-6361/201015362; and v4.0 at the FITS specification page);
- OGIP memo OGIP/93-001; and
- CDS's Standards for Astronomical Catalogues, Version 2.0.
- The VOUnits syntax. This is now the standard unit syntax for the Virtual Observatory, and intended to be as compatible as possible with the existing syntaxes (see section 2.12.1 of the specification for discussion of compatibility). The syntax is specified by the VOUnits specification.

The library includes a set of `known units', which draws heavily on the QUDT specification and models, in the sense that it incorporates a subset of the QUDT units, with a few astronomy-specific additions. Specifically it draws on QUDT v1.1, which was the current version at the time v1.0 of this library was released.

Further links:

- The canonical home page is `https://purl.org/nxg/dist/unity` (please use this URI, rather than the one it redirects to, when citing the library)
- For source and jar downloads for specific versions, see the downloads page.
- For the code, and to report problems, see the repository and bug-parade.
- Video for an overview presentation at CODATA SciDataCon-IDW Seoul 2022: Session ‘Digital Unit Representation Systems and their Use in Infrastructure’ (doi:10.5281/zenodo.6943128)

Documentation:

- For discussion and build instructions, see the README.
- C library (generated using `doxygen`; download).
- Javadocs (download).
- Various grammar files and test cases.
- See the release notes.

You can cite v1.0 of the library using:

    @software{unity-1.0,
      author       = {Gray, Norman},
      title        = {Unity: multi-syntax unit parsing},
      month        = may,
      year         = 2014,
      version      = {1.0},
      doi          = {10.5281/zenodo.6949818},
      url          = {https://doi.org/10.5281/zenodo.6949818}
    }

Cite the ‘latest version’ with DOI 10.5281/zenodo.6949817

Norman Gray
2023 October 22