In the last five years, design patterns have become extremely important in computer science. The reason they are important is that if you identify distinct common patterns, these patterns can then be re-used. Presented here is another design pattern that explains the evolution of most broad technologies like COM+.

The evolution design pattern is really a meta-pattern, a pattern about patterns. It describes how implementations are often aggregated into designs with a common framework. Once this common framework is established it is then possible to add new functionality across all the implementations. This can best be explained with a couple of pictures. Generally, implementations are originally designed in isolation. Each implementation is like an island

This may seem like a far-fetched example, but in reality, it closely emulates what happens in a software development project. Because each implementation is developed in isolation, it becomes next to impossible for a developer working on one implementation to help on any other implementations. As developers begin turning over (leaving the company for greener ($) pastures), new developers either within the same company or new hires, have a difficult time learning this extremely proprietary implementation. The implementation topples over.

To the rescue, comes the architect who points out that if the implementation used a common framework, then one developer could easily move from implementation to implementation without having to re-learn all from scratch. In this new paradigm, the implementations do not exist as islands, as they are no longer implemented in isolation. Now the implementations are dunes on top of a much large island.

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