The following three constraint types are currently limited to accepting individual items as parameter values with [[ https://www.wikidata.org/wiki/Property:P2305 | P2305]] ("item of property constraint"), leading to the creation of large, incomplete, and difficult-to-maintain constraints. Allowing the use of [[ https://www.wikidata.org/wiki/Property:P2308 | P2308]] ("class") as a constraint parameter would allow many of these constraints to be smaller, more complete, and easier-to-maintain.
**Constraint type:** [[ https://www.wikidata.org/wiki/Help:Property_constraints_portal/None_of | none-of (Q52558054)]]
Example: [[ https://www.wikidata.org/wiki/Property:P2408#P2408$ddf48e58-4ec0-b8ef-3e10-b8812ba1ec1d | This constraint ]] has 33 values of "item of property constraint", which could all be replaced with P2308 = [[ https://www.wikidata.org/wiki/Q15275719 | recurring event (Q15275719) ]]. [[ https://query.wikidata.org/#%23None-of%20constraints%20by%20number%20of%20%22item%20of%20property%20qualifier%22%20values%0ASELECT%20%3FQualStatement%20%3Fcount%20WHERE%20%7B%0A%20%20%7B%0A%20%20%20%20SELECT%20%3FQualStatement%20%28COUNT%28%3Fitem%29%20AS%20%3Fcount%29%0A%20%20%20%20WHERE%20%7B%0A%20%20%20%20%20%20%3FProperties%20p%3AP2302%20%3FQualStatement.%0A%20%20%20%20%20%20%3FQualStatement%20ps%3AP2302%20wd%3AQ52558054.%0A%20%20%20%20%20%20%3FQualStatement%20pq%3AP2305%20%3Fitem.%0A%20%20%20%20%7D%0A%20%20%20%20GROUP%20BY%20%3FQualStatement%0A%20%20%7D%0A%20%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22.%20%7D%0A%7D%0AORDER%20BY%20DESC%28%3Fcount%29 | This query ]] gives more such constraints.
**Constraint type:** [[ https://www.wikidata.org/wiki/Help:Property_constraints_portal/Conflicts_with | conflicts-with (Q21502838)]]
Example: [[ https://www.wikidata.org/wiki/Property:P710#P710$79adc499-488a-908f-6824-2e962a373c5e | This constraint ]] has 30 values of "item of property constraint", most or all of which could be replaced with P2308 = [[ https://www.wikidata.org/wiki/Q83267 | crime (Q83267) ]] and P2308 = [[ https://www.wikidata.org/wiki/Q171558 | accident (Q171558) ]]. [[ https://query.wikidata.org/#%23None-of%20constraints%20by%20number%20of%20%22item%20of%20property%20qualifier%22%20values%0ASELECT%20%3FQualStatement%20%3Fcount%20WHERE%20%7B%0A%20%20%7B%0A%20%20%20%20SELECT%20%3FQualStatement%20%28COUNT%28%3Fitem%29%20AS%20%3Fcount%29%0A%20%20%20%20WHERE%20%7B%0A%20%20%20%20%20%20%3FProperties%20p%3AP2302%20%3FQualStatement.%0A%20%20%20%20%20%20%3FQualStatement%20ps%3AP2302%20wd%3AQ21502838.%0A%20%20%20%20%20%20%3FQualStatement%20pq%3AP2305%20%3Fitem.%0A%20%20%20%20%7D%0A%20%20%20%20GROUP%20BY%20%3FQualStatement%0A%20%20%7D%0A%20%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22.%20%7D%0A%7D%0AORDER%20BY%20DESC%28%3Fcount%29 | This query ]] gives more such constraints.
**Constraint type:** [[ https://www.wikidata.org/wiki/Help:Property_constraints_portal/Item | item-requires-statement (Q21503247)]]
Example: [[ https://www.wikidata.org/wiki/Property:P3980#P3980$e5b5dd2f-4402-6c3a-1328-414f0b1a8f89 | This constraint ]] has 39 values of "item of property constraint", most of which could be replaced by P2308 = [[ https://www.wikidata.org/wiki/Q4220920 | filmmaking occupation (Q4220920) ]]. [[ https://query.wikidata.org/#%23None-of%20constraints%20by%20number%20of%20%22item%20of%20property%20qualifier%22%20values%0ASELECT%20%3FQualStatement%20%3Fcount%20WHERE%20%7B%0A%20%20%7B%0A%20%20%20%20SELECT%20%3FQualStatement%20%28COUNT%28%3Fitem%29%20AS%20%3Fcount%29%0A%20%20%20%20WHERE%20%7B%0A%20%20%20%20%20%20%3FProperties%20p%3AP2302%20%3FQualStatement.%0A%20%20%20%20%20%20%3FQualStatement%20ps%3AP2302%20wd%3AQ21503247.%0A%20%20%20%20%20%20%3FQualStatement%20pq%3AP2305%20%3Fitem.%0A%20%20%20%20%7D%0A%20%20%20%20GROUP%20BY%20%3FQualStatement%0A%20%20%7D%0A%20%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22.%20%7D%0A%7D%0AORDER%20BY%20DESC%28%3Fcount%29 | This query ]] gives more such constraints.
In the case of at least one property, the size and number of existing constraints may be causing performance issues: [[ https://www.wikidata.org/wiki/Property_talk:P31#Broken_templates ]]
This task replaces T340761.