We need to flag to users if there are constraint violations in SDC statements.
On Wikidata, users are shown
- a flag icon to warn if a statement fails a constraint requirement identified as having constraint status (P2302) = suggestion constraint (Q62026391), and
- an lightning flash icon if a statement fails a constraint requirement identified as having constraint status (P2302) = mandatory constraint (Q21502408),
- an exclamation mark icon if a statement fails a constraint requirement without a specified constraint status
Additionally, an explanatory message can be specified to show with the warning icon, via constraint clarification (P6607)
It is important for such warnings to become visible, and soon, to flag up immediately to users that particular patterns of usage are inappropriate, or have not yet been agreed by the community.
This is particularly urgent now that we are on the brink of a vast number of more properties becoming available and going live into mass usage on Commons SDC.
Use-case example, presenting why we need this as soon as it can be done, in this comment below.