Rest Post is described in detail here Rest Services In MDriven - but one thing that was added after the initial implementation is the ability to execute actions in Rest Post.
Actions added before any attributes in the root ViewModelClass will be executed before the values sent in are applied.
Other actions in the root ViewModelClass will be executed after the values are applied.
This way you can use top actions to look up things based on url coded variables - and then use actions at the bottom to act on applied data
See details on OCLOperators RestPost page.