The proxy design pattern separates data and code in smart contracts into proxy and logic contracts. Data resides in proxy contracts, while code is sourced from logic contracts. This pattern allows for flexible smart contract development, enabling upgradeability, extensibility, and code reuse. Despite its popularity and importance, there is currently no systematic study to understand the prevalence, use scenarios, and development pitfalls of proxies. We present the first comprehensive study on Ethereum proxies. To gather a dataset of proxies, we introduce PROXYEX, the first framework to detect proxies from bytecode, achieving over 99% accuracy. Using PROXYEX, we collected a dataset of 2,031,422 Ethereum proxies and conducted the first large-scale empirical study. We analyzed proxy numbers and transaction traffic to understand their current status on Ethereum. We identified four proxy use patterns: upgradeability, extensibility, code-sharing, and code-hiding. We also pinpointed three common issues: proxy-logic storage collision, logic-logic storage collision, and uninitialized contracts, creating checkers for these by replaying historical transactions. Our study reveals that upgradeability isn't the sole reason for proxy adoption in DApps, and many proxies present issues like storage collisions and uninitialized contracts, which enhances the understanding of proxies and guide future smart contract research on the development, usage, quality assurance, and bug detection of proxies.

Heterogeneous data fusion from disparate geospatial sensors has drawn increasing attention in multimedia. Unfortunately, environmental sensors are usually sparsely and preferentially located, which restricts situation recognition of geographical regions and results in uncertainty in derived inferences. Spatial interpolation is an effective way to solve the problem of data sparsity, which demands the availability of related data sources. However, these data sources are usually in different resolutions, distributions, scales, and densities, which poses a major challenge in data integration. To address this problem, we present a novel spatial interpolation framework to incorporate diverse data sources and model the spatial processes explicitly at multiple resolutions. Spectral analysis is deployed to generate features at multiple spatial resolutions and to improve the interpolation accuracy at unobserved locations. A statistical operator based on the spatial Gaussian process is implemented and integrated into a geospatial situation recognition system, which can analyze heterogeneous spatio-temporal data streams derived from sensors. To verify the effectiveness and efficiency of the proposed framework, this framework is applied to the PM2.5 air pollution application. Experiments conducted in California, USA, demonstrate that the proposed method outperforms state-of-the-art approaches.

Recent multimedia research has increasingly focused on large scale multimodal data from disparate geospatial sensors. In addition to the volume of the data, the diversity and granularity of the data poses a major challenge in extracting meaningful and actionable information. To address this, we present a novel spatial interpolation framework, capable of incorporating multimodal data sources and modeling the spatial processes comprehensively at multiple resolutions. The framework transforms the spatial interpolation problem into a graph structure learning problem, based on the latent structure of the data. This enables more efficient and accurate predictions at unobserved locations. We demonstrate the effectiveness of our approach by testing it on air pollution interpolation.

EventShop is an open-source software which provides a generic infrastructure for the analysis of heterogeneous spatio-temporal data streams. Efficient interpolation of data from spatially sparse sources is critical but currently missing in EventShop. To address this challenge, we implement a Spatial Gaussian Process based statistical operator into the EventShop framework. Spectral analysis is employed to generate features at higher spatial resolution and to improve interpolation accuracy at unsampled locations. Further, we test this operator by interpolating air pollution levels in California. The evaluations of multiple metrics demonstrate that our operators outperform earlier EventShop operators, chemical transportation models, and state-of-the-art methods.