After some product discussions, I am happy to go with entityschemaid and get this rolling

I fail to see how inventing a brand new data value type solves @Pintoch’s concern that it should use the same data value type as other entities.

In T339920#9037984, @Lucas_Werkmeister_WMDE wrote:

I fail to see how inventing a brand new data value type solves @Pintoch’s concern that it should use the same data value type as other entities.

To me as well, it would make sense that wikibase-entityid would be more conductive to a seamless integration with existing tools.

To elaborate a bit more – I’m worried that creating a new data value type, instead of using either of the suitable existing data value types (string or wikibase-entityid), will actually create more work for tool developers. It’s much rarer for us to create new data value types than new data types – I think this 2015 snapshot of Special:ListDatatypes already contains all the data value types we have today (string, entity ID, globe coordinate, monolingual text, quantity, time). And I think the comments by @Pintoch and @Tpt in the on-wiki discussion support this as well.

Yes, if it was unclear from my comments I can try to clarify again here. From an API user perspective my preferences are (from most preferred to least preferred):

1. wikibase-entityid datavalue type, for consistency with the targeted user experience (EntitySchemas being entities themselves)
2. string datavalue type, which is inconsistent with the UX but has the benefit of being an established datavalue type, which any existing API client library is bound to support already (Wikidata-Toolkit, Wikibase-SDK, pywikibot, …)
3. A new datavalue type, which will likely require some light changes in most API client libraries, and perhaps lead to failures of various severities until those changes are made (for those which have not anticipated the introduction of new datavalue types)

Based on the discussions that we have had over the last weeks, and the request for a product decision to be made; the best option from our side would be wikibase-entityid as it would maintain consistency with other Semantic Entities, ensure a good UX and allow tools to be easily utilised for EntitySchemas.

The other options considered were :

• string which would present a poor UX and would not require us to make any changes, but could pose issues if this is changed further down the line
• entityschemaid which would require tool builders to adapt their tools to a new data value type

I will update the ticket accordingly, thank you all so much for your help and patience on this.

Personally I will oppose wikibase-entityid since EntitySchema is not a type of Wikibase entity. EntitySchema is a completely independent extension.

(striken 2023-08-29; see T344609#9124706)
(reinstated 2023-10-18; see T344609#9260423)

In T339920#9104838, @Bugreporter wrote:

Personally I will oppose wikibase-entityid since EntitySchema is not a type of Wikibase entity. EntitySchema is a completely independent extension.

That is a technical implementation detail which is in principle independent of the question of the product requirement of what API should be available to the users. This task here is purely about the product requirement.
That being said, making EntitySchema a proper Wikibase Entity is certainly one sensible way of doing this, though not exactly trivial either.

Task Breakdown notes:

• This can be done in a relatively similar way to how senses and forms are registered in Lexeme.
• Nothing seems to obviously break, but this is just from a quick glance at the code, it seems like we might not need to rely on any new services in Wikibase.
• We can start by changing the data type in the DT registration and start trying to fix any faulty or broken classes.
• We don't really see any immediate opportunities to parallelize work on this, however, if anything emerges we might create new sub-tasks as we go along.

Change 953672 had a related patch set uploaded (by Lucas Werkmeister (WMDE); author: Lucas Werkmeister (WMDE)):

[mediawiki/extensions/EntitySchema@master] Make EntitySchemaId implement EntityId

https://gerrit.wikimedia.org/r/953672

Change 953687 had a related patch set uploaded (by Lucas Werkmeister (WMDE); author: Lucas Werkmeister (WMDE)):

[mediawiki/extensions/EntitySchema@master] Support EntityIdValue in EntitySchemaFormatter

https://gerrit.wikimedia.org/r/953687

As a reminder: Changing the meaning of wikibase-entityid value type to include non-Wikibase entities is a breaking change and should be announced per https://www.wikidata.org/wiki/Wikidata:Stable_Interface_Policy (adding a new type of Wikibase entity is not breaking, but adding a non-Wikibase entity is); Adding a new value type is only significant change, not breaking.

As the EntitySchemas project is in a short hiatus, I am removing the relevant tickets from the board