super(SYMBOL, BooleanType.BOOLEAN);
}
protected FunctionSignature[] signatures() {
final FunctionSignature[] s = new FunctionSignature[2];
Type strq = TypeRegistry.safeGet("xs:string?");
s[0] = new FunctionSignature(getName(), new Type[] { strq, strq });
s[1] = new FunctionSignature(getName(), new Type[] { strq, strq, StringType.STRING });
return s;
}