Does any application exist that implements the OpenDocument format  and supports "custom schemas"? Please note that I distinguish between the OpenDocument format and applications that implement it, and although OpenDocument does support custom schemas, I do not know if any applications (such as Open Office) exist that implements this feature.

It is quite easy to apply custom schemas in, for example, MS Word 2007 (which does not implement OpenDocument) and edit and modify a document visually within that word processor in such a way that the document will always conform to the custom schema. I would just like to make sure whether this is possible in any application (such as Open Office) that implements the OpenDocument format