[jdom-interest] Schema validating!

[skeens]

Hopefully this makes sense:

I want to validate my document using schema. I've seen all the questions about how to do validation but I'm not assured that the XML document I get contains a schema reference - it will most likely not have one.  

This is where I might be wrong but my understanding is that I can not validate a XML doc. without a DTD or reference to a schema in the XML doc.  Essentially I want to validate the XML I receive with a schema that is not explicately mentioned in the document.
Does any one know how to do this?

Thanks