Looking at https://www.wikidata.org/wiki/Property:P972 and poking around in query.wikidata.org, http://tinyurl.com/y6v9tab7 May I suggest we explore some modest tweaks to the definition, e.g.Instead of "catalog for the item, or, as a qualifier of P528 – catalog for which the 'catalog code' is valid "...say: "a catalog (not necessarily public) which includes the item, or, as a qualifier of P528 – catalog for which the 'catalog code' is valid "Changes:1. (not essential) the "a" just emphasizes that something might show up in several catalogs.2. "not necessarily public" clarifies a more inclusive notion of catalog that would cover grassroots and developing/new projects etc as well as big famous brick-and-mortar collections.3. "includes" rather than "for", again in spirit of (1.).