On the W3C’s public-owl-dev mailing list, Jeremy Carroll mentioned an example that involved the set of documents that import at least four ontologies. I’ve been wanting to look at some data on hoe people are using owl:imports for a while and this prompted me to do it. Swoogle has data on just over 2.3M RDF documents it’s found on the web. These include about 11K imports relations. If we ignore a handful of documents that import RDF, RDFS or OWL, there are 6661 unique documents that import at least one documents and 1613 documents that are imported by at least one document.
How common is it for a document to import many ontologies? Not very, it turns out. Of documents that import any at all, 71% import just one, 89% import one or two and 97% import five or fewer. The five documents that import the most ontologies are these: