Thread Transparency in Information Flow Middleware

Applications that process continuous information flows are challenging to write because the application programmer must deal with flow-specific concurrency and timing requirements, necessitating the explicit management of threads, synchronization, scheduling and timing. We believe that middleware can ease this burden, but middleware that supports control-flow centric interaction models such as remote method invocation does not match the structure of these applications. Indeed, it abstracts away from the very things that the information-flow centric programmer must control. We are defining Infopipes as a high-level abstraction for information flow, and we are developing a middleware framework that supports this abstraction directly. Infopipes handle the complexities associated with control flow and multi-threading, relieving the programmer of this task. Starting from a high-level description of an information flow configuration, the framework determines which parts of a pipeline require separate threads or coroutines, and handles synchronization transparently to the application programmer. The framework also gives the programmer the freedom to write or reuse components in a passive style, even though the configuration will actually require the use of a thread or coroutine. Conversely, it is possible to write a component using a thread and know that the thread will be eliminated if it is not needed in a pipeline. This allows the most appropriate programming model to be chosen for a given task, and existing code to be reused irrespective of its activity model.