On Design

The most important thing to learn about design is that it’s all about trade-offs. There are no perfect designs. Every design has a down side, some draw drawback that will cause difficulties. The is true for all kinds of design whether it’s a building, an organization, a user interface, or software.

Since all designs have problems, the designers job is not to get rid of all problems in the design, it’s to decide which problems are the least costly to have, or which problems are most likely to cause the least damage to the goal of the product. So, to do design well you have to be able to understand what the options are, what the issues are with each option, and in the particular context you are operating in, which issues are the least harmful.

It’s important to understand this when it comes to software design patterns. Design patterns are just common ways of trading one set of problems for another, with the belief that the new set of problems is better than the old. The only time it makes sense to use a pattern is when you have the particular set of problems it was designed to fix, and you’re better off with the new set of problems it leaves you with. But, in order to make good decisions on this, you’ve got to understand what the problem sets are, and how they affect your particular context.

This is not easy! And it takes experience to do it well. Often, the only way to know what the issues are with a particular design choice is that you’ve done it that way before, and seen what issues came from it. However, studying, practicing, and learning from others can take you a long way. The important thing is to never to be fooled into thinking that there are no drawbacks to a particular design decision.