Wiki of App Models
Wiki of apps in general (web or stand-alone), with both public and private models published.
Databases models change, developers make migrations. API schemas change, developers version them. The understanding of all software systems depends on clear understanding of their models.
While we have a "Wiki" of mathematical proofs (https://proofwiki.org/) exists, a "Wiki" of software applications and their modules, doesn't seem to exist.
In fact, the ecosystems of applications are spread widely: some are modular, and by installing a new extension or module, we're automatically installing new database models and API views. Others are not that modular, and define a lot of models within one application. The idea of "Wiki" of app models, thus, is to take the lowest common denominator of all of that -- namely, "model" (data structure or type), register and document it, regardless of the scope where it occurs -- a plugin, a module, an extension, or an application.
The creation of such wiki would happen in a manner, similar to registering and publishing new packages in package managers -- a developer, who wants to continue publishing the models of their application, would register a namespace for application, including the language, and app name, and then, periodically update the definition of each model, publicly, on the models wiki.
One way of realizing this, would be to reuse and modify a package manager software, that supports authentication and publishing packages, then create a wiki-like UI as front-end for this package manager.