Hi!
In order to fix a compatibility issue (https://phabricator.wikimedia.org/T174930) and make the URI more clean, the URI underlying mwapi: prefix in WDQS queries will be changed to https://www.mediawiki.org/ontology#API/. This URI is not used anywhere in the data, but only to designate parameters for MWAPI services[1].
Since this is not change in data but only in service prefixes/URIs, there should not be any impact except for any queries that may use full URI instead of mwapi: prefix for calling the services - such queries will have to be updated. There's no real reason to do it and I recommend to never do it and follow the examples in the manual[1] instead, but out of the abundance of caution I am announcing this change anyway.
The change will likely be deployed in next Monday, in the usual WDQS deployment window[2].
[] https://www.mediawiki.org/wiki/Wikidata_query_service/User_Manual/MWAPI [2] https://wikitech.wikimedia.org/wiki/Deployments