public boolean isItemRequired() {
        return isPersistPublishedItems() || isPayloadDelivered();
    }
Returns true if an item element is required to be included when publishing an
item to this node. When an item is included then the item will have an item ID
that will be included when sending items to node subscribers.<p>

Leaf nodes that are transient and do not deliver payloads with event notifications
do not require an item element. If a user tries to publish an item to a node
that does not require items then an error will be returned.

@return true if an item element is required to be included when publishing an
        item to this node.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/LeafNode.java