My company is rooted in SGML instead of XML and the problem lies in us exporting books, journals, etc. out of InDesign.

We have had a script written that converts SGML files into XML files so we can import them. But we're being told that a script to convert the XML back into SGML is not doable. Am I wrong in thinking that's not right? If X in SGML = Y in XML for the script then shouldn't it be the same if it was written "backwards?"

Is there anything out there that will convert XML back into SGML so I wouldn't have to deal with the corporate politics?

I welcome any suggestions in the matter b/c we're being squeezed out of being able to do book production because of this. As of now, it's not an option to have the entire company switch to XML (although it's been discussed for future).