I think there are instructions in the quick start guide on how to set up local references.
Name your ds AltitudeDS in the *-ds.xml file.
Now you should be able to look it up anywhere in the jboss vm under java:/AltitudeDS
If you want to look up java:/comp/env/jdbc/AltitudeDS you have to set up a resource reference in a jboss.xml file If you don't, I think jboss will attach the reference to DefaultDS as a default.
Of course you could also remove the hsqldb-ds.xml and name your datasource DefaultDS.