A software product is a thing that features certain functions: showing things, calculating things, making sounds, allowing you to enter things, etc. This sounds terribly technical, but in the end even the greatest application is just based on a bunch of bits and bytes carrying out functions.

Looking at Microsoft Word, you see a lot of things the program allows you to do and which you expect to find: writing a letter, editing photos, printing contents, etc. Let’s call the sum of all these high-level features the functional width of the application. Then, for each of these main features, there are sub-features and sub-sub-features, etc. All the stuff that’s needed to make the main features work. For example, if I want to print out a letter, I need to be able to preview my printout. To make that happen, I need a number of sub-features. This vertical view on features let’s call functional depth.

So defining an application translates into defining the functional width and the functional depth. You need both dimensions. The question is: what’s the sequence? Should I start with the width or the depth? Here are the pros and cons for both alternatives.   

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