DirectToWeb in Practice
The DirectToWeb framework includes the inference engine and stock components designed to access information contained in the inference engine.
It is important to note right off that there is really no such thing as a "DirectToWeb Application" despite the common practice of calling the default projects created by using the D2W project template in Xcode "DirectToWeb" applications. In reality, the project templates that refer to "D2W Application" included in WOLips, are simply referring to a WebObjects application that has had the D2W related frameworks linked in by default. In fact, you can leverage D2W in any WO application by linking in the relevant frameworks and then using the components in your pages (or as your pages).
DirectToWeb does not generate code. It uses the inference engine combined with templates for pages and display components to determine behaviour and rendering. The application that is created by using the default D2W project template has very simple and generic behaviours and appearance. When customization is required, the developer can make changes at the rule level, the template (page) level, or at the component level. Learning the most appropriate place to intervene is the crux of the new learning curve that you have embarked on!
D2W dynamically generates web applications based on rules that are matched, evaluated and executed in a context. The context continuously tracks the state of the application and its related data. Rules do not have to perform simple assignments. They can perform more complex assignments using KVC or they can even use custom assignment subclasses.