David Barnes @ Packt

The centerpiece of Dan Roam's excellent book The Back of the Napkin is his visual codex. It helps you to choose the right kind of picture for anything that you want to show:

Even if you use words instead of pictures, the framework is very useful... it doesn't matter much whether you want to describe something in words or shapes.

When an author introduces a concept to a reader they usually describe what the concept is either at a simple or elaborate level. You can see this right in the top left hand corner of the diagram... a (word) portrait of whatever the concept is. You're telling the reader what the concept is. Just about every Wikipedia article is like this -- it goes into reasonable detail, describing the topic.

But that's only one way. And when the concept is unfamiliar, it might be one of the worst approaches. Today I've been trying to get a grip on what F# (the programming language) is all about. I can find plenty of descriptions, clearly aimed at beginners, but none of them really help me. That's not because they're bad descriptions -- but because a description is not the right approach.

Here are some other possibilities:

• A comparison -- show how the new concept is similar to and different from something the reader already knows. So a simple comparison of how F# is different from or similar to VB.NET or C# would help me get a handle on it. If you're introducing a technical concept to a non technical person, compare it to something in the real world.
• Show where the concept fits in with familiar problems and ideas. This could be as simple as saying "F# is perfect for...." and then listing certain kinds of application. This helps me put F# on "the map" that I carry around in my head.
  
• Show how it fits into a process. This is like flowchart, where one of the components is F#. "Say you want to build an application that [blank]. You realize it will need the following features: [.......]. When you come to build the app, you use F# because [show how F# offers a great fit with the requirements].
• Show why it's useful. "F# will help reduce development time in the following circumstances [.......] because it [......].

This is a case where choosing what to say is more important than the way you say it. Even a poorly written comparison might be far more useful to the average reader than a polished, perfect description.