Platform UI Command Design
Starting point for menu and toolbar placement of commands.
Commands and Handlers
Commands are managed by the org.eclipse.ui.commands extension point and the ICommandService.
Handlers are managed by the org.eclipse.ui.handlers extension point and the IHandlerService.
KeyBindings and Contexts
KeyBindings are managed by the org.eclipse.ui.bindings extension point and the IBindingService.
Contexts are managed by the org.eclipse.ui.contexts extension point and the IContextService.
Currently, menus are managed by 4 extension points:
Programmatic contributions are managed through a number of locations: IActionBars, IViewSite, IEditorSite ... more to follow
The Contribution proposal started a couple of releases ago Contribution RFC
There are discussions in a number of places: