Does sphinx support the use of GR-XML grammars, or do I have to convert my existing grammar to the java speech grammar format?
Does sphinx support the use of GR-XML grammars
Yes, see Dialog demo in latest version sphinx4-5prealpha
http://cmusphinx.sourceforge.net/wiki/tutorialsphinx4
or do I have to convert my existing grammar to the java speech grammar format?
No