assert elementStack.peek().equals("bonehierarchy");
String boneName = attribs.getValue("bone");
String parentName = attribs.getValue("parent");
Bone bone = nameToBone.get(boneName);
Bone parent = nameToBone.get(parentName);
parent.addChild(bone);
} else if (qName.equals("bone")) {
assert elementStack.peek().equals("bones");
// insert bone into indexed map
bone = new Bone(attribs.getValue("name"));