Can I quickly prototype my own custom format for an XML document? So for example, I know that under the hood Word docs are basically XML formatted docs.

Is there a way that I can build my own custom XML tags and prototype my own custom XML document format? Something like:

<CustomGraphXMLtag>somevaluehere<CustomGraphXMLTag> <somenewtag2>some other value</> ........

Can I do this with Apache OpenOffice SDK or any other way?