Serverless computing offers fine-grained billing and elastic scalability, making it appealing for workflow execution. However, it also suffers from cold-start latency and stricter execution constraints. In contrast, traditional serverful cloud resources, such as virtual machines, provide coarser provisioning granularity but benefit from relatively lower unit cost. This work explores the potential of blending serverful and serverless resources to harness their complementary strengths for cost-effective workflow execution. We propose a hybrid resource management framework that dynamically allocates workflow tasks across both types of resources. A Budget-constrained Workflow scheduling algorithm for Blended cloud (BWB) is developed to minimize makespan while respecting user-specified budget. Evaluation experiments are conducted under real-world cloud settings by using realistic workflow applications. BWB is compared against state-of-the-art approaches for serverful, serverless, and blended clouds. Experimental results show that BWB consistently outperforms its state-of-the-art peers, achieving makespan reductions ranging from 10.6% to 37.6%, thereby demonstrating the cost-effectiveness of blending cloud resources for workflow execution.

Community detection refers to mechanisms that aim to identify groups of interacting nodes in a network according to the structural properties of the network. It has been used to analyze various graphs. In the context of social networks, it requires the collection of each user's social relations, posing the risk of user privacy intrusion caused by untrusted servers. Local differential privacy is a widely adopted approach for providing privacy protection while allowing acceptable utility of the protected data for analytics. There has been growing research interest in applying local differential privacy protection to community detection. However, such protection approaches typically suffer from poor accuracy due to the excessive noise in the protected data. This paper proposes LDP-Cd, a two-phase community detection framework under local differential privacy. LDP-Cd initializes the community groups using the Louvain community detection algorithm and iteratively refines the community in the second phase. Besides, we propose an order-consistent data perturbation method over the degree vector, thus ensuring the ordering consistency of the fitness between the user and community groups, thereby improving the accuracy of community detection. Experimental results on real datasets show that LDP-Cd has significant advantages over existing methods regarding community detection accuracy and a trade-off between user privacy and community detection utility.

Collecting users’ historical data such as movie watching and music listening, and mining frequent items from them, can improve the utility of smart services, but there is also a risk of compromising user privacy. Local differential privacy is a strict definition of privacy and has been widely used in various privacy-preserving data collection scenarios. However, the accuracy of existing locally differentially private frequent items mining methods decreases significantly with the increase in the dimensions of data to be collected. In this paper, we propose a new locally differentially private frequent item mining method for high-dimensional data, which decreases the dimension used for data perturbation by grouping the contents and improving the interference matrix generation method, so as to improve the data reconstruction accuracy. The experimental results show that our proposed method can significantly improve the accuracy of frequent item mining and provide a better trade-off between privacy and accuracy compared with existing methods.

Analyzing the popularity of microblogging services is of great significance in various applications. The number of posts provides novel insights into the popularity of microblogging services, and is critical to learn about the frequency of use. Existing approaches analyze this parameter by observing posts published by a large number of users, which may lead to underestimate the value since the sampled user may stop to use the service during the observing process. In this paper, we propose a novel method to estimate the number of posts in microblogging services. The basic idea behind this method is to make use of a common API provided by microblogging services, i.e., the public_timeline API. Posts sampled by this API may duplicate among multiple invocations, so the capture-recapture model can be used to estimate the total number of posts. Based on the traditional capture-recapture model, we propose an improved model to address challenges on low sampling probability and unequal sampling probability. We validate the proposed method using a real life Sina Weibo dataset, and the experimental results demonstrate the effectiveness and accuracy of our proposed method.