As the development of network technologies, the network conference is gradually accepted by the people and has become the major option for remote conference. In unified communication (UC), users have multiple terminals and multiple communication and coordination manners, such as participation in a multimedia conference, instant message chatting, internet telephone or intra-enterprise phone call. For example, in a multimedia conference (including voice and network), users may use mobile phone, fixed-line phone, IP phone, and network telephone client, etc. to access a voice conference, and may also use personal computer or smart mobile phone terminal to access a network conference. During the conference, users may talk, share contents, listen and chat with typing, etc. Furthermore, in the current UC technology, different states, such as busy state, and idle state, etc., of users in different communication manners may be registered in a presence server so that other communication calls or session managers may be aware of some states of the current users.
However, in many cases, the real-time activities and actual states of users in the above various communication manners are not presented in the presence server. For example, if other users have subscribed the current state of a user being in conference, these other users may only see the state that the user is in a conference (or in a telephone conversation), although in the conference that may last several hours, the user may be sometimes in talking, sometimes in listening, or sometimes in chatting with typing. Some relatively advanced UC systems may expand the current state, while detect the activities of a user in conference, and determine whether the user is currently in a busy state or an idle state based on the active states of the user. If the user is in an idle state, the UC systems may allow other communication manners to be used for conversation with this user. However, such improvement requires not only addition of corresponding detecting and judging modules (or rules engine), but also expansion of the presence server at the same time. Furthermore, in practice, users may have multiple states in different conferences or in different moments of a conference, it is impossible to make changes to the presence server for the addition of each of the states, and at the same time, and sometimes excessive states are unnecessary, since not every subscriber is interested in tiny changes of states. In addition, although privacy of states is defined in the specifications of the presence servers, namely, some states may be visible to certain users, while some states are invisible, this also needs pre-configuration.