1. A system comprising: a memory; and a processor in communication with the memory to implement: a Web container to provide a runtime environment for a deployed application; and a Web container extension (WCE) provider to implement a Web container extension, the WCE provider configured to provide services to the deployed application and the Web container by using the WCE as a communication interface between the WCE provider, the Web container and the deployed application, the WCE including a Web container extension application programming interface (WCE API) that receives values from a first one of the Web container, the deployed application and the WCE provider and provides corresponding values to a second one of the Web container, the deployed application and the WCE provider, the WCE provider configuring the WCE to relate the received values to a model for a runtime architecture and to provide the corresponding values based on the runtime-architecture model, the Web container creating a WCE identifier to unregister the WCE during a stopping of the services, and the Web container deploying the WCE in the runtime environment for the deployed application based on a determination that: a web archive file contains at least one deployment descriptor for the WCE; a descriptor map of the web archive file includes the WCE provider; and the WCE provider is registered with the runtime environment.