LH Tools is a WordPress plugin that enables a sparql endpoint for for WordPress sites. This will enable semantic querying of WordPress data either from the site itself or from external providers of RDF triples.
Whilst this can be used on a standalone basis, it is most useful when combined with the other LH (LocalHero) plugins:
LH RDF: https://lhero.org/plugins/lh-rdf/
Which exposes a large part of the WordPress data as semantic rdf content
LH Relationships: http://localhero.biz/plugins/lh-relationships/
Which enables semantic linking between wordpress posts, pages, categories, and other objects.
This plugin relies on the Arc2 RDF library, originally written by Ben Nowack. ARC is a flexible RDF system for semantic web and PHP practitioners.
Download LH-Tools from the WordPress Plugin Directory.