Facets: Fast comprehensive mining of coevolving high-order time series

Mining time series data has been a very active research area in the past decade, exactly because of its prevalence in many high-impact applications, ranging from environmental monitoring, intelligent transportation systems, computer network forensics, to smart buildings and many more. It has posed many fascinating research questions. Among others, three prominent challenges shared by a variety of real applications are (a) high-order; (b) contextual constraints and (c) temporal smoothness. The state-of-the-art mining algorithms are rich in addressing each of these challenges, but relatively short of comprehensiveness in attacking the coexistence of multiple or even all of these three challenges. In this paper, we propose a comprehensive method, FACETS, to simultaneously model all these three challenges. We formulate it as an optimization problem from a dynamic graphical model perspective. The key idea is to use tensor factorization to address multi-aspect challenges, and perform careful regularizations to attack both contextual and temporal challenges. Based on that, we propose an effective and scalable algorithm to solve the problem. Our experimental evaluations on three real datasets demonstrate that our method (1) outperforms its competitors in two common data mining tasks (imputation and prediction); and (2) enjoys a linear scalability w.r.t. the length of time series.