There are quite a few web frameworks that target the development of realtime web applications. Mostly, however, the solution is by providing an API that allows developers to push/receive messages from/to an open channel.
Though this kind of API offers an opportunity to get started doing Realtime Web, it doesn’t offer a programming model for dealing with the challenges encountered when programming with streams of data, including creating, adapting, manipulating, filtering and merging streams of data and all of the synchronization involved.