The Direct to Web framework is a configurable system for creating WebApplications from a model
All Direct to Web needs to create the application is an  object model, which you can build using EOModeler.

The applications created are not static. Instead, Direct to Web uses information from the model at runtime to dynamically generate the pages. Consequently, you can modify your application’s configuration at runtime using the Direct to Web Assistant (WebAssistant for short). You can hide entities, hide their properties, reorder the properties, and change the way they are displayed without recompiling or relaunching the application.

You can also "freeze" part (or all) of the application, those parts of the application that are frozen become static java code using the internal WebFramework of WebObjects, and can be modified directly by altering the generated java code or the generated html code.

It is very similar to TheNakedObjectsFramework (more or less the same concept), but for WebApplications.

More on Direct2Web In 
*** http://developer.apple.com/documentation/WebObjects/Developing_With_D2W/index.html ( BrokenLink )