private static Pattern getNamespacePattern(String directive) {
        return Pattern.compile("^(" + directive + "\\s*=\\s*)(([a-z][a-z0-9_]*)+([.][a-z][a-z0-9_]*)*)$");
    }
This class generates a tree of CNodes from a .def file.

@author gjoranv
@author hmusum
configgen/src/main/java/com/yahoo/config/codegen/DefParser.java