Data Streaming Model

* Data streaming model is a fundamental software architecture, which has wide applications in the field of data processing. This model is based on the following basic ideas for the embedded applications:
- Multi-threading
- Object-oriented: components

* Components
A component is a hardware-independent, software abstraction of a hardware or microcode function. It has its own interface that performs component specific functions. Components are the basic units to construct a data stream or data flow. A component could be associated with a thread or not. Two key features for components are inheritance and polymorphism and dynamic creation and linking. Dynamic creation means components must be dynamically allocated at startup or runtime instead of global or local allocation. Dynamic creation and linking make application and low-level supports, like middleware, separated as much as possible.

* Types of Components
- Stream filter
It is the processing element (brick) in a data stream. In general, it is associated with one thread. It has input/output ports and command/message ports for async events.
- Stream connection
It is used to connect two or more stream filters to construct a data stream (mortar). In essence, a stream connection is a message queue. In general, no thread is bond with stream connections. Therefore, the comm. among tasks is implemented with message passing instead of shared data structure. This model might be more suitable for multi-core application since it helps to hide the existence of other cores.
- Buffer factory
It is used to manage memory usage within a data stream. One or more buffer factories could be associated with one flow as needed. No threads are with them.
- Flow controller
This macro component creates, initializes and connects multiple building components as mentioned above to construct a data flow. Also it is the interface to the higher application level and emits commands to and receives status messages from the whole flow. It could be considered to be a special case of stream filters.

New components are created and old components might be deleted when a new data flow is built, in order to efficiently make use of memory. However, some kinds of components provide facilities for all data streams, so they need to be created once at startup and stay in the whole system lifetime.