The prevalent heterogeneous Graph Neural Network (GNN) models learn node and graph representations using pre-defined meta-paths or only automatically discovering meta-paths. However, the existing methods suffer from information loss due to neglecting undiscovered meta-structures with richer semantics than meta-paths in heterogeneous graphs. To take advantage of the current rich meta-structures in heterogeneous graphs, we propose a novel approach called HeGTM to automatically extract essential meta-structures (i.e., meta-paths and meta-graphs) from heterogeneous graphs. The discovered meta-structures can capture more prosperous relations between different types of nodes that can help the model to learn representations. Furthermore, we apply the proposed approach for text classification. Specifically, we first design a heterogeneous graph for the text corpus, and then apply HeGTM on the constructed text graph to learn better text representations that contain various semantic relations. In addition, our approach can also be used as a strong meta-structure extractor for other GNN models. In other words, the auto-discovered meta-structures can replace the pre-defined meta-paths. The experimental results on text classification demonstrate the effectiveness of our approach to automatically extracting informative meta-structures from heterogeneous graphs and its usefulness in acting as a meta-structure extractor for boosting other GNN models.

With the development of global positioning technology, sensor networks and smart mobile terminal, a large number of trajectory data are accumulated. Trajectory data contains a wealth of information, including spatiality, time series, and other external descriptive attributes (i.e., features, travelling mode, etc.). Trajectory analysis and mining show the great value. The research of trajectory similarity measurement is the basis of trajectory data management and mining, which plays an important role in trajectory computing. Most trajectory similarity work only focuses on the spatial-temporal features. The addition of multi-attributes to the trajectories changes the trajectory similarity. However, there are few researches focusing on multi-attributes trajectory similarity. In this paper, we propose two novel trajectory similarity measurements, i.e. MMTD (Maximum-Minimum Trajectory Distance) and SUMTD (Sum of minimum Trajectory Distance) and analyze the correlation among the spatial-temporal similarity and textual similarity. Finally, the measurement validity is verified and visualized through clustering by both a simulation dataset and a real dataset.

As a fundamental technology in intelligent transportation systems (ITS), accurate traffic flow prediction has emerged as a critical challenge in real-time applications. How to fully utilize the traffic data, and capture the spatial temporal correlation are keys to improve the model's prediction ability. Numerous neural networks have been proposed to address this issue. However, most of these existing methods have the following two problems: 1) Lack of byroads information. Meaning that the existing methods do not consider the byroads in real-life traffic environments; 2) Lack of potential learning ability. Meaning that the existing methods suffer the non-similar forgetting and hard to gain the multi-hop correlation. To overcome these problems, we propose a novel Spatial Temporal Byroad-Aware Graph Convolution Network (ByGCN) in this paper. ByGCN consists of byroad identification and spatial temporal learning modules. In the first module, we design spatial temporal decoupling and graph diffusion blocks to identify the byroads and reconstruct them into the flow data. In the second module, with the help of spatial temporal attention and GCN, our module can capture the complex spatial temporal correlation. Experiments on four real-world traffic datasets demonstrate that ByGCN outperforms the state-of-the-art methods.

Location-based social networks have been widely used. However, due to the lack of effective and safe data management, a large number of privacy disclosures commonly occur. Thus, academia and industry have needed to focus more on location privacy protection. This paper proposes a novel location attack method using multiple background options to infer the hidden locations of mobile users. In order to estimate the possibility of a hidden position being visited by a user, two hidden location attack models are proposed, i.e., a Bayesian hidden location inference model and the multi-factor fusion based hidden location inference model. Multiple background factors, including the check-in sequences, temporal information, user social networks, personalized service preferences, point of interest (POI) popularities, etc., are considered in the two models. Moreover, a hidden location inference algorithm is provided as well. Finally, a series of experiments are conducted on two real check-in data examples to evaluate the accuracy of the model and verify the validity of the proposed algorithm. The experimental results show that multiple background knowledge fusion provides benefits for improving location inference precision.