What is a model?
George and I build models. It says so on our new business cards. So what is a model?

BTW, we are not the only ones who build models. We all build models, you probably build really good models and more often than you think. They may not be in Excel and may not be presentable on a PowerPoint slide... but you have built and used models... sometimes to save your own life.

Let me take driving as an example to illustrate two very important aspects of a good model.

1. A model is NOT reality, but a representation of reality.
2. A model is "good" or "bad" based on the purpose of the model.

You adhere to these key rules of good model building when you drive. We discus the first aspect in this entry.

A model is only a representation of reality. There is an apocryphal story about a king who wanted to create the best map of his kingdom. He commissioned a task force that was mandated to create the most accurate map of his kingdom. It was to show everything so there would be no mistake and confusion as to what was in his kingdom.

With this mandate, the task force went to work. After a few weeks, the king demanded to see the work in progress. They brought him their "latest version", rolling it in on a cart. As they started to unfold the huge map, the king realized that the map was "actual size". It started with his court, and showed where the throne was, depicted in the same size as the throne. It showed what the floor looked like, and every location of every wall and column.

This was not a good map. This is not a good model. It may be accurate, but it's impractical (among other things).

When you drive, you are constantly building, using and rebuilding models in your mind to run "projections" and ready yourself for or to directly take actions.. Will that car move over to my lane? Do I need to cover my brake? You use a "map" in your head to plot out where you need to go. You incorporate this info with your knowledge of physics, how a car operates, your state (are you in a rush or are you enjoying a leisurely ride?) and many more elements to help you drive.

Whew! To illustrate the first aspect of modeling... have you realized that your model is not reality? It's only in your mind. It's also probably filled with incorrect and incomplete information. And yet you rely on this as you make your way down the streets and highways. This incomplete, sometimes inaccurate model, is used by you and the other drivers as each of you go about your driving day.

Good thing, too. You have learned to only include things in your model that is needed, to abstract and simplify things. In my next post, I will continue by talking about the second aspect of "what is a model".
- posted by hcpark @ 10:22 AM