Lucas_Werkmeister_WMDE added a comment.
In T358310#9571351 <https://phabricator.wikimedia.org/T358310#9571351>, @Jony wrote: > @Bugreporter it’s possible, please see T220602 <https://phabricator.wikimedia.org/T220602> That was a change between external identifier and string, which is the only supported conversion according to Help:Data type § Changing datatype <https://www.wikidata.org/wiki/Help:Data_type#Changing_datatype>. (Strictly speaking, that page only says that changing //from// string //to// external identifier is possible, while that task changed it the other way around; changing from external identifier to string is just less common.) Other data type changes behave differently, generally somewhere between “not useful” and “completely broken”. Changing between Item and Lexeme is on the “not useful” end of the spectrum, in my opinion. You can technically do it and the software won’t completely blow up (at least as far as I can tell – I haven’t tested all corner cases), but there’s just no sensible interpretation of any existing statements that were created with the old data type. I tried this out locally, and in the UI, it gets shown as “Invalid value”: F42060791: Screen Shot 2024-02-23 at 11.14.05.png <https://phabricator.wikimedia.org/F42060791> In the JSON, you get a very confusing combination of `datatype` and `datavalue.value.entity-type`: { "datatype": "wikibase-lexeme", "datavalue": { "value": { "entity-type": "item", "numeric-id": 50, "id": "Q50" }, "type": "wikibase-entityid" } } In RDF, you get values of both types, which would probably confuse some external data reusers: wd:P603 a wikibase:Property ; wdt:P603 wd:Q50, wd:L3 ; I wouldn’t want to unleash mixed-value statements like that on Wikidata, so IMHO the only safe situation where you could change a data type between Item and Lexeme would be a property that isn’t used in //any// statements yet – not even on itself – and in that case you might as well just delete and recreate the property. So I completely agree with @matej_suchanek: let’s just recreate the property. TASK DETAIL https://phabricator.wikimedia.org/T358310 EMAIL PREFERENCES https://phabricator.wikimedia.org/settings/panel/emailpreferences/ To: Lucas_Werkmeister_WMDE Cc: Lucas_Werkmeister_WMDE, matej_suchanek, Bugreporter, Aklapper, hoo, Jony, Danny_Benjafield_WMDE, Astuthiodit_1, karapayneWMDE, Invadibot, maantietaja, ItamarWMDE, Akuckartz, Nandana, Lahi, Gq86, GoranSMilovanovic, QZanden, KimKelting, LawExplorer, _jensen, rosalieper, Scott_WUaS, Wikidata-bugs, aude, Lydia_Pintscher, Mbch331
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