Saturday, November 18, 2006

Application interaction models

I have assembled the interaction types I want to make possible in the near future. They assume a similar architecture to the one verified in current Web Applications, that is, a client-server architecture, a standard (mainstream) browser running on the client and an application container of your choice running on the server. But, unlike today's regular usage of this architecture, I want to allow some other application interaction models:

  • Client-Server code mobility, where the server may detect it is unable to compute every requested operation, and sends some of the (possibly still running) computations to the client for it to finish them. As I depict in the preceding diagram, after the client knows the code to the computation he needs to finish, it can gain the ability to perform it without accessing the server (unless there is some server-side information that needs to be fetched, obviously).

  • Disconnected Execution. This sort of interaction is interesting as the client is able to work while being offline (or at least, disconnected from the server). The only requirement is that all of the functionality (perhaps organized in functional modules) and the related domain data must be fetched from the server: As one can see, this may pose other challenges, such as domain data access control (e.g., I may not be able to have full control to some objects that were being used by the server to produce the interface, and thus I cannot have that (whole) object on the client side).
  • Server replication, to grant reliability in the provided application. While there are several approaches to do server replication, all of them must allow messages that arrive to a front-of-the-line server to be replicated to all others (or at least the effects of processing the received message). This can be done by the exchange of continuations (see the Termite approach, in my previous posts).
  • Inter-client interactions are the most uncommon model, when compared to existing uses of Web Applications. In the "several interactions" arrows can be two main types of communication. There can be only data exchange, like in instant messaging, white-boards or on-line games. But there may also be execution flow exchange. You can have two clients making parallel computations, in a sort of collaborative processing. You can also have ubiquitous execution, like having a smart-phone "pick up" the application execution from the desktop computer's browser and carrying on with it.
While this list may not be complete, it is my starting point. Off course I'll add more examples or complete/modify the existing ones if I see it necessary.

Have a nice weekend!