"Document" is a bit of a troublesome word. It implies that you can communicate out into the void, and whoever reads it will understand a series of perhaps compl

"Document" is a bit of a troublesome word. It implies that you can communicate out into the void, and whoever reads it will understand a series of perhaps complex choices. You probably want a model, not a picture. Visio is useful for making pictures -- diagrams. You want something that is a purposefully-simplified version of a much more complex system for purposes of communication/decision-making. Something that can be manipulated. Something to help facilitate conversations around certain narrow issues in a complicated system. That's a model. There is a great post right now on HN about MVC. In it, there are some UML models. Check it out. They're not documentation of a system. They're isolated "cut-outs" to facilitate discussion around one area. There are a bunch of great modeling tools. Many are being mentioned here. Go check them out! The big thing to understand is the difference between a diagram and a model -- and making deliberate decisions both about what to include and exclude in each thing you share. BTW, you can also use physical materials to model. The secret to good modeling is the simplification-mapping, not necessarily the model substrate being used.