“Today, you can download a tool that you can use to describe the concepts in a problem domain as the basis for a modeling tool or graphical designer. It is itself a graphical tool built on top of our designer platform and it is completely integrated into Visual Studio. For example, if you need a business process modeling tool, this editor allows you to describe the concepts specific to the way you like to model your business processes.”

It is basically a graphical designer hosted in Visual Studio 2005 for designing and editing the concepts (or metamodel) of visual domain specific languages.

There is also an interesting : “Walkthrough of the Microsoft Tools for Domain Specific Languages“ showing the use of the object model for a user interaction process (UIP) chart language. UIP chart defines pages and transitions between them as part of the design of a Web site, a wizard, or a form-based application. Figure 1 is an example of a UIP chart for a fictitious online shopping Web site. You might find more information on this page about the User Interface Process (UIP) Application Block - Version 2.0.

Read more about it on MSDN, on the Domain Specific Language (DSL) Tools page.
Download the tool, on Microsoft® Tools for Domain Specific Languages Technology Preview October 2004 Release page.