In Figure 1, there is a single channel to the top-level program in a set of inter-related programs. The set of programs within the shaded area can be regarded as a "component". The client program "sees" only the external channel and has no knowledge of the processing that takes place, nor of the existence of the back-end programs.
Inside the component, the programs can pass the channel between themselves. Alternatively, a component program could, for example, pass a subset of the original channel, by creating a new channel and adding one or more containers from the original channel.