To be explicit [software design]

Software is an odd medium in which to construct something. Because few physical forces make you design one way or another, many design decisions sadly resist any form of objective analysis. Where design counts is often not in how the software runs but in how easy it is to change. When how it runs is important, ease of change can be the biggest factor in ensuring good performance. This drive toward changeability is why it´s so important for a design to clearly show what the program does-and how it does it. After all, it´s hard to change something when you can´t see what it does. An interesting corollary of this is that people often use specific designs because they are easy to change, but when they make the program difficult to understand, the effect is the reverse of what was intended