Semantic wikis have become an increasingly popular means of collaboratively managing Knowledge Graphs. They are powered by platforms such as Semantic MediaWiki and Wikibase, both of which enable MediaWiki to store and publish structured data. While there are many semantic wikis currently in use, there has been little effort to collect and analyse their structured data, nor to make it available for the research community. This paper seeks to address this gap by systematically collecting structured data from an extensive corpus of Semantic-MediaWiki-powered portals and providing an in-depth analysis of the ontological diversity (and re-use) amongst these wikis using a variety of ontological metrics. Our paper aims to demonstrate that semantic wikis are a valuable and extensive part of Linked Open Data (LOD), and in fact may be considered an own active “sub-cloud” within the LOD ecosystem, which can provide useful insights into the evolution of small and medium-sized domain-specific Knowledge Graphs.

The Semantic Web initiative has established standards and practices for publishing interconnected knowledge, where RDF Schema and OWL shall enable the reuse of ontologies as one of these established practices. However, Wikibase, the software behind Wikidata, which is increasingly gaining popularity among data publishers, lacks the functionality to import and reuse existing RDF Schema and OWL ontologies. To facilitate ontology reuse, FAIR data publishing and encourage a tighter connection of existing Linked Data resources with Wikibase instances, we align the Wikibase data model with RDF and present O2WB, a tool for ontology import and export within Wikibase.