protected static RDFNode getUnique(Resource root, Property property) {
List<RDFNode> nodes = root.listProperties(property).mapWith(getObject).toList();
if (nodes.size() == 0) return null;
if (nodes.size() == 1) return nodes.get(0);
throw new NotUniqueException(root, property);
}
protected void checkType(Resource root, Resource type) {
if (!root.hasProperty(RDF.type, type))
throw new CannotConstructException(this.getClass(), root, type);
}
protected static Statement getUniqueStatement(Resource root, Property property) {
List<Statement> statements = root.listProperties(property).toList();
if (statements.size() == 0) return null;
if (statements.size() == 1) return statements.get(0);
throw new NotUniqueException(root, property);
}