Data Mining - Concepts and Techniques.

Statistics for Spatial Data.

Even though human movement and mobility patterns have a high degree of freedom and variation, they also exhibit structural patterns due to geographic and social constraints. Using cell phone location data, as well as data from two online location-based social networks, we aim to understand what basic laws govern human motion and dynamics. We find that humans experience a combination of periodic movement that is geographically limited and seemingly random jumps correlated with their social networks. Short-ranged travel is periodic both spatially and temporally and not effected by the social network structure, while long-distance travel is more influenced by social network ties. We show that social relationships can explain about 10% to 30% of all human movement, while periodic behavior explains 50% to 70%. Based on our findings, we develop a model of human mobility that combines periodic short range movements with travel due to the social network structure. We show that our model reliably predicts the locations and dynamics of future human movement and gives an order of magnitude better performance than present models of human mobility.

/pdf/friendship-and-mobility-user-movement-in-location-based-2u0rrxuc9l.pdf

Friendship and mobility: user movement in location-based social networks

The theory of affordances

A great variety of systems in nature, society and technology -- from the web of sexual contacts to the Internet, from the nervous system to power grids -- can be modeled as graphs of vertices coupled by edges The network structure, describing how the graph is wired, helps us understand, predict and optimize the behavior of dynamical systems In many cases, however, the edges are not continuously active As an example, in networks of communication via email, text messages, or phone calls, edges represent sequences of instantaneous or practically instantaneous contacts In some cases, edges are active for non-negligible periods of time: eg, the proximity patterns of inpatients at hospitals can be represented by a graph where an edge between two individuals is on throughout the time they are at the same ward Like network topology, the temporal structure of edge activations can affect dynamics of systems interacting through the network, from disease contagion on the network of patients to information diffusion over an e-mail network In this review, we present the emergent field of temporal networks, and discuss methods for analyzing topological and temporal structure and models for elucidating their relation to the behavior of dynamical systems In the light of traditional network theory, one can see this framework as moving the information of when things happen from the dynamical system on the network, to the network itself Since fundamental properties, such as the transitivity of edges, do not necessarily hold in temporal networks, many of these methods need to be quite different from those for static networks

Temporal Networks

http://www.cs.ucy.ac.cy/~dzeina/papers/infosys16-proxplus.pdf

Crowdsourcing emergency data in non-operational cellular networks

Short Cuts for Traversals in Object-Oriented Database Systems

Mobility of user poses new challenges to research on spatial data access. Spatial data cached in the mobile client may become invalid because of the movement of the client. To increase the reusability of the cached data, we can identify the valid scope of the spatial data (i.e., the spatial area within which the data is known to be valid) and save the valid scope as well as the data in the cache. In this paper, we study issues on the dissemination of spatial data and valid scopes in a wireless environment. We investigate methods for representing valid scopes and their impacts on system performance. A generic representation method, called the invalidation-efficiency-based (IEB) method, is proposed. Simulation experiments are conducted to compare the performance of IEB with other representation methods. Result shows that IEB is superior to the other methods because it tries to balance the precision and overhead of valid scopes.

Selecting the best valid scopes for wireless dissemination of location-dependent data

The social presence theory in social psychology suggests that computer-mediated online interactions are inferior to face-to-face, in-person interactions. In this paper, we consider the scenarios of organizing in person friend-making social activities via online social networks (OSNs) and formulate a new research problem, namely, Hop-bounded Maximum Group Friending (HMGF), by modeling both existing friendships and the likelihood of new friend making. To find a set of attendees for socialization activities, HMGF is unique and challenging due to the interplay of the group size, the constraint on existing friendships and the objective function on the likelihood of friend making. We prove that HMGF is NP-Hard, and no approximation algorithm exists unless \(P=NP\). We then propose an error-bounded approximation algorithm to efficiently obtain the solutions very close to the optimal solutions. We conduct a user study to validate our problem formulation and perform extensive experiments on real datasets to demonstrate the efficiency and effectiveness of our proposed algorithm.

Maximizing Friend-Making Likelihood for Social Activity Organization

Much research has been conducted using web access logs to study implicit user feedback and infer user preferences from clickstreams. However, little research measures the changes of user preferences of ranking documents over time. We present a study that measures the changes of user preferences based on an analysis of access logs of a large scale digital library over one year. A metric based on the accuracy of predicting future user actions is proposed. The results show that although user preferences change over time, the majority of user actions should be predictable from previous browsing behavior in the digital library.

/pdf/measuring-user-preference-changes-in-digital-libraries-tj79l5jluy.pdf

Wang-Chien Lee

Papers

Crowdsourcing emergency data in non-operational cellular networks

Short Cuts for Traversals in Object-Oriented Database Systems

Selecting the best valid scopes for wireless dissemination of location-dependent data

Maximizing Friend-Making Likelihood for Social Activity Organization

Measuring user preference changes in digital libraries