[Wikidata-l] ontology Wikidata API, managing ontology structure and evolutions

Hi, a problem seems (not very surprisingly) to emerge into Wikidata : the managing of the evolution of how we do things on Wikidata. Properties are deleted, which made some consumer of the datas sometimes a little frustrated they are not informed of that and could not take part of the discussion. My question is : is it a community problem, a technical problem, or both ? IMO it is a very serious problem for a project of the size of Wikidata that just leaving to humans to make notifications to whoever uses te datas could be a disaster. We therefore need to have tools to manage that, part of the solution is from the technical side. I'll try to do a review of which tools we have now, as tools, to make notifications from people who want to make a change that imacts other projects or people, and interestec projects or people: * Purely human : someone who make a change in a model or delete a property is responsible to notify every projects he knows would be impacted. This is tedious and imperfect, and imperfectly pass through language barriers, if he has to notify every Wikipedias. * Using watchlists : This is a semi automated process. Every people involved into a project, model, or property has to follow the relevant pages. Still imperfect for many reasons. * Using the notify extensions, like the ping projects or ping user templates, interproject, this may need software solutions from the developper of the Echo Mediawiki extensions Another, and complemnetary solution is to mantain data or models API and versions, as we do in sotfware API, and manage versioning, parralel versions, deprecations ... but this is ressource consuming. Any ideas ? I thing it's an important question we need to give answers, at least partial ones.