https://github.com/citation-style-language/schema/ is the official repository for the Citation Style Language (CSL) schema.
The CSL schema consists of the files:
CSL styles and locale files can be validated against csl.rnc, which incorporates the contents of the other four files.
In addition, the repository contains the files csl-data.json and csl-citation.json, which describe the metadata model used by citeproc-js for its input data and for embedded citation data in word processor documents, respectively. At this point these JSON schemas are not yet normative.
For more information, see CitationStyles.org.