I've spent a bit of time creating a Relax NG schema for use within our team to validate XML documents we use for exchanging information. The schema is not complicated, but it is reasonably large.

I am wondering if there exists a tool that can read in such a Relax NG schema and assist a user in creating a corresponding instance document, using the schema as a template. Perhaps an application with a GUI that creates fields and drop-down selections for each part of the document?

For example, the tool might create an outline XML document and prompt the user to select multiples of certain elements, fill in each field, perhaps with permitted values read directly from the schema. It might also show the user via visual feedback when their document is 'complete', or highlight validation problems as they come up.

I could anticipate writing a custom GUI tool to create such an XML document, but I'd really like changes to the schema to be automatically reflected by the GUI - and I really wonder if this hasn't already been done.

I know some editors can automatically validate an XML document against a schema as it's being written, but I would really like to get my users one step away from the XML so they don't have to worry about the details of the XML syntax.