Mauro Regio and Víctor García Aprea wrote a great article about Guidance Automation Toolkit and Domain-Specific Language Tools for Visual Studio 2005: Integration Scenarios on MSDN.
The Microsoft Guidance Automation Package (GAT) and Domain-Specific Language Tools for Visual Studio 2005 (DSL) are two key technologies in Microsoft's software-factory strategy that allow architects and developers to author and package guidance and domain-specific languages.
GAT and DSL offer considerable value when used separately. However, when used together, they complement each other and, more importantly, can make up for certain limitations that each technology might have in its current state.
This paper presents a few GAT/DSL integration scenarios and discusses the benefits of adopting them, how to combine the two technologies, and whether you need to develop significant code development to do that.