How to Grow a System

We have the luxury of treating software like that. A bridge is not like that; there is never a baby bridge, but merely an unfinished bridge. Bridges are a lot simpler than software.

It is good to think of software as growing, because it allows us to make useful progress before we have a perfect mental image. We can get feedback from users and use that to correct the growth. Pruning off weak limbs is healthful.

To do this, you must visualize the end result and communicate it in a way that the engineering team can get excited about. But you must also communicate to them a path that goes from wherever they are now to where they want to be with no large leaps. The tree must stay alive the whole time; it cannot be dead at one point and resurrected later.

This approach is captured in spiral development. Milestones that are never too far apart are used to mark progress along the path. In the ultra-competitive environment of business, it is best if the milestones can be released and make money as early as possible, even if they are far away from a well-designed endpoint. One of the programmer’s jobs is to balance the immediate pay-off against future pay-off by wisely choosing a growth path expressed in milestones.

A reader, Rob Hafernik, sent in this comment on this section that I can do no better than to quote in full:

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