Microsoft Visio is a data diagramming application that can be used for schematic or measured drawings. Visio is a general purpose tool that can be customised for particular tasks to focus the user’s attention. It can also be programmed to create diagrams automatically from data supplied to it. The user can create many different categories of drawings with Microsoft Visio, but the ones I am interested in are those that contain data. Visio can provide a graphical representation of data, and it can be used to create it. This book is neither a beginner’s guide to Visio—plenty of them should be around—nor is it a tutorial for graphic artists. Instead, it is intended for those who want to represent or model data visually, and for the myriad of budding developers who want to set up categories of drawings for others to use. Before we get into the nitty-gritty of this, we should take a moment to check that you have a basic understanding of the anatomy of Visio. Without this, you may go off on a road to nowhere.