A method, system, and computer program product for managing a managing a middleware architecture is disclosed. As such, a plurality of specification levels can be managed concurrently within a same runtime. An application manager and a set of runtime execution stacks are established to form a middleware. The application manager is configured to establish an interface to the set of runtime execution stacks. The runtime execution stacks are configured to run independent of one another using representative specification technology runtimes. A request to start an application is received. The application includes an application manifest. A particular runtime execution stack of the set of runtime execution stacks on which to run the application is determined. The determination is made based on the application manifest and the representative specification technology runtimes. Using the particular application runtime execution stack, the application is started.