ActiveWriter is basically a tool to model entities and relations between them. It consists of a modeller and a code generator. Entities are generated as C# or VB classes.

There are many tools to generate classes from diagrams, and ActiveWriter is not the best of them if it's only the class generation. What makes it useful is that, you can instruct it to decorate generated code with necessary ActiveRecord attributes. This way, you can instantly persist your entities to a database, retrieve them and walk through them using entity relations.