The previous sections describe how you can create a new module or
toolset by starting from an empty base class and adding all the functionality
that you need. Alternatively, you may find that you want to use most of the
functionality of an existing module or toolset. If a suitable module or toolset
exists, it may be easier for you to derive a new module or toolset from it and
then add or remove functionality from it. This chapter describes how to make
various modifications to an existing module or toolset.