21. The method according to claim 20 , further comprising: obtaining event change history information from the resource content publishing device; storing the obtained event change history information in a storage, and sending a link to the event change history information to a subscriber device subscribing to the predetermined event topic, in order for the subscriber device to obtain the event change history information via the link.
20. A method to implement an intermediate connected between a resource content publishing device and a subscriber device in a real-time communication for resource content, comprising: receiving, by the intermediate, identification information of a subscriber device from the subscriber device; receiving, by the intermediate, an event topic selected by the subscriber device based on an event topic list, wherein, the identification information comprises path information of a topic path created by the subscriber device for receiving a notification event related to the selected event topic, the event topic selected by the subscriber device is a complex event topic set constituted by at least two separate event topics, and the intermediate device comprises a complex event processing apparatus for processing a complex event; adding the identification information of the subscriber device and the selected event topic to an event topic subscription search table; determining whether an event topic of new resource content obtained by the resource content publishing device belongs to the complex event topic set; creating a complex event by applying a predefined rule describing a relation between the separate events related to the complex event topic set onto the new resource content if it is determined that the event topic of the new resource content belongs to the complex event topic set; obtaining based on the search table, the identification information of the subscriber device subscribing to an event topic related to the new resource content when new resource content is available; and sending a notification event including the event topic and the new resource content to the subscriber device.