UML modeling provides extensive support for refactoring your implementation projects. 

Refactoring means rewriting existing source code with the intent of improving its design rather than changing its external behavior. The focus of refactoring is on the structure of the source code, changing the design to make the code easier to understand, maintain, and modify. 

The refactoring features affect both source code and model. As a result, your project is consistent after refactoring, even if it includes UML diagrams. 

The primary resource book on refactoring is Refactoring - Improving the Design of Existing Code by Martin Fowler (Addison - Wesley, 1999).