I am Thad Guidry from Schema.org and Freebase.  We have a need for a new property (or point me to an existing property we can use) that can hold a URL that is the concept of a "external subclass in an external vocabulary" such as Schema.org, etc.

For example: http://schema.org/DataDownload is a Type we have in Schema.org and we would like to be able to somehow express that "dataset" https://www.wikidata.org/wiki/Q1172284 has an available subclass at http://schema.org/DataDownload ... "a dataset in downloadable form", not just a any old dataset.

The alternative vision that might also work for us could be that "dataset" https://www.wikidata.org/wiki/Q1172284 has an available "external class about this subject").

Whichever view that Wikidata deems more worthy (or an alternate view that you can think of), either one I think will work for our Schema.org mapping (equivalent/sub/super classes and properties, etc) within Wikidata.  We have begun adding mappings to Wikidata entities and properties this week to help solve and close an outstanding issue we have here: https://github.com/schemaorg/schemaorg/issues/280

Please provide your thoughts to this message or leave feedback in our Github issue.

Thank You!