The guidelines for policy-based designs boil down to managing the complexity and making sure the ends justify the means—the flexibility of the design and the elegance of the resulting solutions should justify the complexity of the implementation and its use.
Since most of the complexity comes from the increasing number of policies, this is the focus of most of the guidelines. Some policies end up putting together very different types that happen to have a similar implementation. The goal of such a policy-based type is to reduce the code duplication. While a worthwhile objective, this is generally not a good enough reason to expose a multitude of disparate policy options to the end user of the type. If two ...
