While looking working on my recent WikiCrowd project I ended up looking at the ontological tree of both Wikidata entities and Wikimedia Commons categories.
In this post, I’ll look at some of the ontology mappings that happen between projects, some of the SPARQL that can help you use this ontology in tools, and also some tools to help you explore this complex tree.
I’m using trains as I think they are fairly easy for most folks to relate to, and also don’t have a massively complex tree.
Commons & Wikidata mapping
Depicts questions in WikiCrowd are entirely generated from these Wikimedia Commons categories, such as Category:Trains & Category:Steam locomotives. These are then mapped to items on Wikidata such as Q870 (train) & Q171043 (steam locomotive).
Wikimedia Commons categories quite often contain infoboxes on the right-hand side that link to a variety of resources for the thing the category is covering. And quite often there is a Wikidata item ID present, this is the case for the categories above.
Likewise on Wikidata statements for P373 (Commons category) will often exist for entities that are depicted on Commons.