Mediawiki Extension Semantic Mediawiki
Like Mediawiki Extension Cargo it allows storing of data that can then be queried. Unlike Cargo, information can be stored in a tag-like format, even if the data is not declared anywhere. This can be very flexible. Also, SMW has implemented some ways to format results of queries that are not available in Cargo. Since Cargo already uses templates to store data, it is easy to add the storage of SMW to the same template as well, even long after the template is created.
As of 2021 SMW has fallen behind in full compatibility with the newest versions of Mediawiki, and it now requires composer to install. Since most of the functionality is also available in Cargo we have mostly stopped using SMW in new projects.