throw new SparqlEmptyException("Variables missing from xml");
}
for (int i = 0; i < variables.getLength(); i++) {
Node variable = variables.item(i);
if (variable == null) {
throw new SparqlParseException("Variable in head parsed as null");
}
String varName = ((Element)variable).getAttribute("name");
if (varName == null) {
throw new SparqlParseException("Variable in head has null value");
}
this.variables.add(varName);
}
}