if (getProductionCount()<=0)
violations.addViolation("No productions are defined", location);
for (Enumeration e = productions.elements(); e.hasMoreElements(); )
violations.addViolations(((Production) e.nextElement()).validate());
SymbolSet ntsymbols = getSymbols().getNonterminals();
for (int i = 0; i<ntsymbols.getSymbolCount(); i++)
if ( !contains(ntsymbols.getSymbol(i)))