The IDE already supports creating XML documents constrained by a DTD or XML Schema, but not by a RelaxNG schema.

Creation of such documents, if implemented, should of course come with the typical benefits of such association - namely, context dependent suggestions for nodes and values and a validation option.

Due to the lack of any standard link from an XML file to an associated RelaxNG file, the associations should be defined as part of the project instead. Ideally, there would also be a "global" level RelaxNG associations by an XML namespace, PLUS the "project" level associations between an RelaxNG file, and a folder/file to which it overrides any global settings.