Our approach in this book has been to provide tools for thinking about the important questions involved in open source adoption. So far, we have looked at approaches for evaluating the maturity of open source, determining the skills of an IT department, and understanding the fully loaded costs of using open source. One more such tool, a taxonomy of IT systems, is required to help discover the right areas in which to apply open source.
This taxonomy sorts the IT systems into three categories: stable, flexible, and dynamic.
Stable systems are those for which the business requirements are well understood and are unlikely to change in any unanticipated way. A payroll system is a good example of a mission-critical stable system. Every year or so there are new tax tables, but the system doesn’t need to be rewritten to accommodate them. Legacy applications that have been doing the same job for 20 years are another example of a stable system. Simple weblog analysis is yet a third example of a stable system.
Flexible systems are those that are changed once every couple of years. Flexible systems are configured or customized to a small degree to solve a problem, and then they are left alone. A simple collaboration system such as a discussion forum, email list manager, or basic weblog system is a good example of a flexible system. It must be installed and then adapted to meet a need, and every so often it is reconfigured as needs change.
Dynamic systems ...