1. A method implemented at least in part by a computer, the method comprising: obtaining a copy of a source XML (Extensible Markup Language) document, the source XML document including configuration data for use by an application in conjunction with the application executing in an environment; obtaining a transformation document that includes declarative statements that indicate modifications to make to the copy to transform the copy into a target XML document, the transformation document also including location information that indicates nodes in the copy upon which the modifications are to operate; transforming, within an integrated development environment, the copy of the source XML document according to the transformation document to create the target XML document, a first declarative statement of the transformation document indicating a file and an element of the copy, the file including additional declarative statements that indicate one or more modifications to make to the element of the copy, transforming the copy including applying the one or more modification to the element of the copy; and providing the target XML document; and wherein the copy and the transformation document have an identical schema that expresses constraints on structure and content of the copy and transformation document, the constraints additional to constraints imposed by XML.