A recent O'Reilly Network article about using WebObject's "Direct To Web" technology by Josh Paul got me thinking about a new term: RBRAD, or "Rule Based Rapid Application Development."
Direct To Web debuted a few releases ago in WebObjects, and it basically builds a full web application for data management based on an EOModel (the object model mapped to a data source using Enterprise Objects Framework). I played with a demo of WebObjects a couple of years ago and was stunned by D2W. I was expecting a full WebObjects application to be generated, complete with .wo (the HTML components) and class files for all of the different class views. Instead, I got a self contained application that generated all of the HTML views and handled the web actions, based on the model and a corresponding set of rules - there was basically no "generated code" that I could see. And the generated application is fairly rich, but it's primarily targeted at one purpose: publishing a corporate database on the web.
To a lesser degree (or greater, depending on ones point of view), I've been seeing this take off everywhere. In particular, the Workflow Engine in the Zope Content Management Framework alone can be used to build custom applications just by writing new rules - either by writing full Python workflow agent components, or by using a through-the-web tool to define states and transitions and all their rules and constraints. Other rule engines found their way into the CMF core, and Plone has built itself on this framework and runs even further with the concept. In particular, add ons like Archetypes and Portal Transforms (and I'm sure there are others) can all be grafted together to build fairly complex content/data driven applications that share a common user interface and whose model and view layers are as much (or more) controlled by the collaborating rule engines as anything else. Other systems, such as Struts, seem to be applying similar principles on the Java side.
We've been playing with various systems along this path in house, most of them home grown. There's a lot to be done, but the benefits have been staggering thus far.