External control 

     A pattern for mapping hierarchical structures 
          to external control mechanisms

                   Guntram  Berti
                     BTU Cottbus
                   
                     October 1998

Controlling parameters is a necessity in every non-trivial application.
We present a pattern that aids in decoupling external control mechanics 
from the internal component structure, while supporting the automatic 
mirroring of internal structure into external representation.
Furthermore, we show how to use this pattern in the implementation of
a C++ component for stream-based control that has been used successfully
in Scientific Computing applications.