The Pet example illustrates a simple “from scratch” modeled customization with very little (unique/interesting) logic and no (new) associations. There are, not surprisingly, many different kinds of customizations. Some customizations simply extend and existing business class to add properties (a customization largely superseded by Windchill’s soft typing capabilities), some exist to add new associations to existing business objects, some exist to add validation and other logic to existing Windchill classes, and so on. The remaining sections will cover all of the various kinds of customizations, as well as providing greater insight into this customization.