ctx.responseobjects instead of node's
resobjects. Yap use policies for manage security application.
resobjects with additional properties and methods and includes many other "framework" features, such as routing and templating, which Yap does not.
httpnode module, where as Express is an application framework for node.js.
(req, res, next), are incompatible with Yap. Your application will essentially have to be rewritten from the ground, up.