The objective of this tool is saving time. It helps you write use cases and use them as the basis of your design. Everything from your regular editor. If you already have maven you can start working on your use cases almost right away. See the Quick Start UCDD is open source released under the GNU license.
UCDD is a very practical aproach to object modeling. It helps you avoid getting lost on modeling everything. The use cases serve as a guide on what should be modeled. Several types of UML diagrams are needed but the bulk of the work is in the sequence diagrams and that's where you save time with this tool.
XML is standard but most importantly it is text and it can be managed like a regular source file. You can use your favorite IDE and your favorite source code controller.
Working with plain files has another added benefit. Using a graphical tool for design can be counter productive. People usually spend more time making a good looking diagram than actually thinking about the design.
Maven is a great tool to manage your projects. It generates very professional documentation but most of it is related to the java source code. Thanks to maven your analysis and design documents automagically get the same professional look.
UCDD is a methodology where the initial uses cases drive the design of the application.
The idea is that correlating the use cases with the UML sequence diagrams is possible to determine the objects involved, the methods that should be implemented and the way the objects collaborate with others.
The approach is described in detail in the books "Use Case Driven Object Modeling with UML" and "Applying Use Case Driven Object Modeling with UML" authored by Doug Rosenberg and Kendall Scott.