Download the XML Compiler, add the plugin, and then do the following:
- Right click on the project and make sure XML Nature is on
- At the top of the file:
<!DOCTYPE modelglue SYSTEM "modelglue.dtd">
<!DOCTYPE modelglue PUBLIC "-//MODEL-GLUE COM//DTD MODEL-GLUE//EN" "modelglue.dtd">
I just made up the identifiers because there didn't seem to be a real one. I suppose the best one to use is the <!DOCTYPE modelglue SYSTEM "modelglue.dtd"> one as it'll likely never change.