This extension provides plugins that allow CKAN to expose and consume metadata from other catalogs using RDF documents serialized using DCAT. The Data Catalog Vocabulary (DCAT) is "an RDF vocabulary designed to facilitate interoperability between data catalogs published on the Web". More information can be found on the following W3C page:
http://www.w3.org/TR/vocab-dcat
It also offers other features related to Semantic Data like exposing the necessary markup to get your datasets indexed in Google Dataset Search.
For details visit the official documentation under github.com/ckan/ckanext-dcat
Changes were made to read the custom DCAT triples used by NOMAD and DSMS data sources.