Network reachability analysis on temporally varying interaction networks

The Internet has become one of the most important elements in our daily lives. There are plenty of interactive applications available for billions of users that provide different kinds of interactions. These user interactions may form an intermittently connected network for information propagation. In such networks, e.g., interactive forum, website, and tweeter-like online social applications, user behavior generally exhibits temporally varying features due to the extensive temporal-spatial diversity and sparsity among user interactions ( such as users´ online/offline activities). It is easy to see that at any time and area, any pair of users in a temporally varying interaction network are not necessarily connected since there may not exist such a path between them. Usually each piece of information between them is transmitted intermittently at different discrete time series, and thus, form a path in a chronological order.