Processes Are Data : A Programming Model for Distributed Applications

Applications in distributed environments must scale to an increasing number of concurrently active application instances. Today’s application servers spend a significant amount of resources on reliably managing state for these instances, turning them into data management servers instead of process servers. The goal of the Demaq project is to overcome the limitations of these systems using a novel programming model for applications based on asynchronous messaging (e.g. Web Services). A crucial aspect of our approach is the representation of state. Messages do not only represent requests and replies sent to and from an application, but retained messages are also used to model the application instance state. This contrasts with most of today’s application servers where two separate data models, languages and stores are used for requests and state. In Demaq, a single, highly efficient, reliable message store is used both for requests and instance state, and a single declarative language specifies message flow and state management. This extends data independence to the whole application stack, thereby improving both developer productivity and - as experimental results confirm - application scalability and performance