Bindings Documentation
Introduction
Complementary to GObjectIntrospection, we could do something like "Documentation Introspection" to collect library documentation (currently generated using gtk-doc) in one place. Language bindings could then generate appropriate documentation based on that using their own tools.
Documentation could either be stored with metadata in .gir files in an own xml namespace or separately.
Implementation
GObjectIntrospection/Doctools is implementing this idea.
Another example (old)
Seed's unofficial instrospection Documentation makes use of this data, This blog post describes how gobject-introspection can be used to generate the documentation, along with linking to the Javascript source code.
Using existing tools
GTK-Doc is currently used to build documentation for libraries. From that, we could import documentation into .gir files with a new gtk-doc module (could be named gtkdoc-mkgir).
Valadoc could be used to write documentation metadata for Vala libraries to .gir files or to xml files along those.
Projects that could make use of Documentation Metadata
Vala - Compiler for the GObject type system
PyGObject - Python bindings
JGIR - Java/JVM bindings
Gjs - Javascript (spidermonkey) bindings