Some Wikidatans have come up with a system of machine readable constraint templates that are added on the talk page. There's a list of these at https://www.wikidata.org/wiki/Category:Properties_with_constraints, and a summary at https://www.wikidata.org/wiki/Wikidata:Database_reports/Constraint_violations/Summary which shows different violations.
Right now bot authors have to write code to manually parse these templates, it would be great if we could have these constraints stored in the data model itself.
The software wouldn't necessarily need to enforce them, just store them.
Whiteboard: u=dev c=story p=0