Change is inevitable. If your system is to last, it must be flexible. Sometimes being prepared for change may be even more important than meeting current requirements. It s impossible to make any system infinitely flexible, so you need to understand the nature of likely changes - being over-ambitious could damage your project too!

There are three main dimensions of flexibility:

• Changing functions, or adaptability,

• Changing workloads, or scalability,

• Changing working environment, or portability.

You may get some idea about expected flexibility when you interview users about their requirements. However, the requirements may be incomplete, mis-prioritised or change during the project. A more successful technique is scenario planning , where you discuss the widest possible range of future scenarios for the business, and then think about how your system would change to meet them. You will have to translate between how the business may change, and the IT implications.

Your aim is to keep future options open, as long as that doesn t unduly impact your project s cost, complexity and risk. Try to design a structure in which the current choices can be changed later, but don t use this as an excuse to paralyse progress by refusing to make any decisions.

Don t tie things together too tightly. This loose coupling is particularly important where two items are at different stages of maturity, or are changing at different rates. Layered and component-based architectures help to separate things...