Reason:
It is not deployed anywhere according to wikiapiary
Barely any code has been since 2012 beside the routine maintenances.
- Archive documentation on mediawiki.org https://www.mediawiki.org/wiki/Extension:Semantic_Expressiveness
- Remove from mediawiki/extensions ( along with in .gitmodules)
- Remove tests in integration/config ( zuul/layout.yaml )
- Remove from translatewiki ( groups/MediaWiki/mediawiki-extensions.txt )
- Empty repository and add a OBSOLETE file.
- Archive the extension's diffusion repository: rESEX
- Mark the repository read-only in Gerrit: https://gerrit.wikimedia.org/r/#/admin/projects/mediawiki/extensions/SemanticExpressiveness
- Delete the GitHub mirror: https://github.com/wikimedia/mediawiki-extensions-SemanticExpressiveness