SymbolSet ntsymbols = getSymbols().getNonterminals();
for (int i = 0; i<ntsymbols.getSymbolCount(); i++)
{
if (!contains(ntsymbols.getSymbol(i)))
violations.addViolation("Nonterminal symbol \""+ntsymbols.getSymbol(i)+"\""+
"is not defined through a production", location);
if (ntsymbols.getSymbol(i).getName().equals("error"))
violations.addViolation("Nonterminal symbol with name \"error\" is not allowed", location);
}