High-quality annotated datasets are crucial for advancing machine learning in medical image analysis. However, a critical gap exists: most datasets either offer a single, clean ground truth, which hides real-world expert disagreement, or they provide multiple annotations without a separate gold standard for objective evaluation. To bridge this gap, we introduce CytoCrowd, a new public benchmark for cytology analysis. The dataset features 446 high-resolution images, each with two key components: (1) raw, conflicting annotations from four independent pathologists, and (2) a separate, high-quality gold-standard ground truth established by a senior expert. This dual structure makes CytoCrowd a versatile resource. It serves as a benchmark for standard computer vision tasks, such as object detection and classification, using the ground truth. Simultaneously, it provides a realistic testbed for evaluating annotation aggregation algorithms that must resolve expert disagreements. We provide comprehensive baseline results for both tasks. Our experiments demonstrate the challenges presented by CytoCrowd and establish its value as a resource for developing the next generation of models for medical image analysis.

Owing to their unprecedented comprehension capabilities, large language models (LLMs) have become indispensable components of modern web search engines. From a technical perspective, this integration represents retrieval-augmented generation (RAG), which enhances LLMs by grounding them in external knowledge base. A prevalent technical approach in this context is graph-based RAG (G-RAG). However, current G-RAG methodologies frequently underutilize graph topology, predominantly focusing on low-order structures or pre-computed static communities. This limitation affects their effectiveness in addressing dynamic and complex queries. Thus, we propose DA-RAG, which leverages attributed community search (ACS) to dynamically extract relevant subgraphs based on the queried question. DA-RAG captures high-order graph structures, allowing for the retrieval of self-complementary knowledge. Furthermore, DA-RAG is equipped with a chunk-layer oriented graph index, which facilitates efficient multi-granularity retrieval while significantly reducing both computational and economic costs. We evaluate DA-RAG on multiple datasets, demonstrating that it outperforms existing RAG methods by up to 40% in head-to-head comparisons across four metrics while reducing index construction time and token overhead by up to 37% and 41%, respectively.

Traffic Signal Control plays a vital role in modern traffic management. However, most existing methods focus exclusively on vehicle flow, neglecting the critical role of pedestrians, leading to suboptimal performance in intersections with mixed vehicle-pedestrian traffic. Pedestrian behavior presents unique challenges due to its irregularity and flexibility, such as non-lane-based movements and uncertain crossing directions, which cannot be modeled by existing methods. To address this limitation, we propose VPLight, a comprehensive framework designed to manage bothVehicle andPedestrian dynamics in traffic signal control. Specifically, we first design the Pedestrian Feature Extractor to capture the spatiotemporal dynamics of pedestrian movement, offering a robust representation of their irregular patterns. Subsequently, to coordinate traffic signal control at multiple intersections, we develop a novel communication approach called V-Comm to enable effective integration among intersections. Extensive experiments show that VPLight outperforms state-of-the-art baselines with significant margins (up to +44.04%). Our results demonstrate that VPLight can remarkably address the challenges of mixed vehicle-pedestrian traffic control and enhance the overall traffic flow efficiency across the road network.

Estimating spatial distributions is important in data analysis, such as traffic flow forecasting and epidemic prevention. To achieve accurate spatial distribution estimation, the analysis needs to collect sufficient user data. However, collecting data directly from individuals could compromise their privacy. Most previous works focused on private distribution estimation for one-dimensional data, which does not consider spatial data relation and leads to poor accuracy for spatial distribution estimation. In this paper, we address the problem of private spatial distribution estimation, where we collect spatial data from individuals and aim to minimize the distance between the actual distribution and estimated one under Local Differential Privacy (LDP). To leverage the numerical nature of the domain, we project spatial data and its relationships onto a one-dimensional distribution. We then use this projection to estimate the overall spatial distribution. Specifically, we propose a reporting mechanism called Disk Area Mechanism (DAM), which projects the spatial domain onto a line and optimizes the estimation using the sliced Wasserstein distance. Through extensive experiments, we show the effectiveness of our DAM approach on both real and synthetic data sets, compared with the state-of-the-art methods, such as Multi-dimensional Square Wave Mechanism (MDSW) and Subset Exponential Mechanism with Geo-I (SEM-Geo-I). Our results show that our DAM always performs better than MDSW and is better than SEM-Geo-I when the data granularity is fine enough.

A modern service model known as the “hub-oriented” model has emerged with the development of mobility services. This model allows users to request vehicles from multiple companies (agents) simultaneously through a unified entry (a ‘hub’). In contrast to conventional services, the “hub-oriented” model emphasizes pricing competition. To address this scenario, an agent should consider its competitors when developing its pricing strategy. In this paper, we introduce DRLPG, a mixed opponent-aware pricing method, which consists of two main components: the two-stage guarantor and the end-to-end deep reinforcement learning (DRL) module, as well as interaction mechanisms. In the guarantor, we design a prediction-decision framework. Specifically, we propose a new objective function for the spatiotemporal neural network in the prediction stage and utilize a traditional reinforcement learning method in the decision stage, respectively. In the end-to-end DRL framework, we explore the adoption of conventional DRL in the “hub-oriented” scenario. Finally, a meta-decider and an experience-sharing mechanism are proposed to combine both methods and leverage their advantages. We conduct extensive experiments on real data, and DRLPG achieves an average improvement of 99.9% and 61.1% in the peak and low peak periods, respectively. Our results demonstrate the effectiveness of our approach compared to the baseline.

Annotation through crowdsourcing draws incremental attention, which relies on an effective selection scheme given a pool of workers. Existing methods propose to select workers based on their performance on tasks with ground truth, while two important points are missed. 1) The historical performances of workers in other tasks. In real-world scenarios, workers need to solve a new task whose correlation with previous tasks is not well-known before the training, which is called cross-domain. 2) The dynamic worker performance as workers will learn from the ground truth. In this paper, we consider both factors in designing an allocation scheme named cross-domain-aware worker selection with training approach. Our approach proposes two estimation modules to both statistically analyze the cross-domain correlation and simulate the learning gain of workers dynamically. A framework with a theoretical analysis of the worker elimination process is given. To validate the effectiveness of our methods, we collect two novel real-world datasets and generate synthetic datasets. The experiment results show that our method outperforms the baselines on both real-world and synthetic datasets.

With the development of ubiquitous smart devices, shared mobility services, such as food delivery, ridesharing and crowdsourced parcel delivery, and the related problems, such as task assignment and route planning have drawn much attention from academia and industry. Specifically, shared mobility services enable one worker to deliver more than one package/passenger together such that their routes can share some common sub-routes. Tardiness (the exceeded time) can harm users' experience and reduce the revenue of workers and platforms, which is not well handled in the existing studies. In this paper, we propose a framework, TrendSharing, to minimize the total tardiness when serving all tasks. In TrendSharing, we first build a flow tree to group tasks together. Then, we propose a concept of trend, which represents a group of tasks with high sharability in the flow tree. Furthermore, we devise a decision factor$\epsilon$-score to properly select the trend from the flow tree. In addition, we devise an indicator k-regret to quantify the likelihood of tardiness for each task and devise a greedy algorithm to conduct task assignment. We observe that the insertion operation that is widely used by existing works has little effect on the objective of minimizing total tardiness. Thus, we adopt a simple yet effective strategy, which will continuously append newly planned routes to the workers' existing routes. Moreover, we design an algorithm to plan a route for the trend with an approximation ratio of 2.5. Through extensive experiments, we demonstrate the efficiency and effectiveness of our proposed approaches on real datasets.

Ridesharing services, such as Uber or Didi, have attracted considerable attention in recent years due to their positive impact on environmental protection and the economy. Existing studies require quick responses to orders, which lack the flexibility to accommodate longer wait times for better grouping opportunities. In this paper, we address a NP-hard ridesharing problem, called Minimal Extra Time RideSharing (METRS), which balances waiting time and group quality (i.e., detour time) to improve riders' satisfaction. To tackle this problem, we propose a novel approach called WATTER (WAit To be fasTER), which leverages an order pooling management algorithm allowing orders to wait until they can be matched with suitable groups. The key challenge is to customize the extra time threshold for each order by reducing the original optimization objective into a convex function of threshold, thus offering a theoretical guarantee to be optimized efficiently. We model the dispatch process using a Markov Decision Process (MDP) with a carefully designed value function to learn the threshold. Through extensive experiments on three real datasets, we demonstrate the efficiency and effectiveness of our proposed approaches.

Urban traffic flow data is useful in transport ap-plications, playing an important role in various tasks such as road planning, site selection, ad services, etc. However, traffic flow data is the composition of personal driving trajectories, which can reveal sensitive information such as home and work locations, leading to privacy issues. Thus publishing traffic flow data while not disclosing private information remains a challenge for urban managers. To address this challenge, we study the noisy publication of traffic flow data in this paper. The noise is added to the data with respect to the differential privacy paradigm, which ensures data safety but deteriorates its utility. On the other hand, we find that the inherent relations of the flow data inherited from the road network structure can be used to correct data without hurting the privacy property. Hence, we propose post-processing techniques, which exploit the data's inherent relations for corrections over the global and local differentially private traffic flow data, respectively. Extensive experiments on real data show that the proposed post-processing techniques improve the data utility by 29.7%-41.1% and 17.3%-48.6% subjecting to the global and local differential privacy paradigm, respectively.

With the rapid development of mobile Internet technology, on-demand car-hailing services have become essential for people's daily commuting. Order dispatch is a critical problem in on-demand car-hailing services. However, in most existing works, the service provider is asked to set a unified pick-up distance to prevent long waiting time for requesters. Indeed, different requesters have different tolerance for pick-up distance, and some requesters may accept longer pick-ups if offered discounts for payment. Regarding this fact, we formulate discount-based order dispatch as a coupling of two subproblems, discount determination and order dispatch, aiming to dispatch more orders and thereby more platform profits. We propose customized methods to solve the problems for shared and non-shared mobility services, respectively. We also conduct extensive experiments to evaluate the effectiveness and efficiency of our proposed methods on a real dataset, which shows that our methods can achieve 170% improvements in non-shard services and 43% improvements in ridesharing services on average in terms of attained profit compared to the widely adopted baselines.

Data collection is indispensable for spatial crowd-sourcing services, such as resource allocation, policymaking, and scientific explorations. However, privacy issues make it challenging for users to share their information unless receiving sufficient compensation. Differential Privacy (DP) is a promising mechanism to release helpful information while protecting individuals’ privacy. However, most DP mechanisms only consider a fixed compensation for each user’s privacy loss. In this paper, we design a task assignment scheme that allows workers to dynamically improve their utility with dynamic distance privacy leakage. Specifically, we propose two solutions to improve the total utility of task assignment results, namely Private Utility Conflict-Elimination (PUCE) approach and Private Game Theory (PGT) approach, respectively. We prove that PUCE achieves higher utility than the state-of-the-art works. We demonstrate the efficiency and effectiveness of our PUCE and PGT approaches on both real and synthetic data sets compared with the recent distance-based approach, Private Distance Conflict-Elimination (PDCE). PUCE is always better than PDCE slightly. PGT is 50% to 63% faster than PDCE and can improve 16% utility on average when worker range is large enough.

Hub-oriented mobility services have gained great developments in recent years, enabling riders to simultaneously call vehicles from multiple mobility-supply companies (agents) on a single APP (which we call "hub"). Competing with others on such a hub, to obtain an order, an agent company first needs to get admitted by the requester, which is in turn affected by its quotation. The quotation needs to be attractively low compared to those of the opposing agents. Thus, an opponent-aware pricing strategy is needed for an agent to play well in the hub scenario, which is rarely discussed in existing works. To address the aforementioned issue, in this work, we first propose a quotation prediction model, which employs a neural network with a customized loss function to predict the opponents’ quotations. Based on the predictions, we then propose multi-arm bandit based methods to decide a proper quotation for the agent, in order to obtain orders while retaining profits. We finally conduct extensive experiments on real data, where the quotation-determining method integrated with the prediction model has achieved a remarkable profit improvement up to 85.5% compared to baseline methods, demonstrating their effectiveness.

Bike-sharing systems, where people rent bikes typically for last-mile commuting, has gained great popularity in recent years due to the rapid development of mobile networks. Station-based bike-sharing systems have been widely studied in both academia and industry, where problems like bike rental demand prediction and bike redistribution have been discussed. In contrast, not much attention has been paid to the routing algorithms for shared-bike riders. A routing solution consists of two stations, suggesting where to rent and return a bike. Existing routing works generally target a single rider. However, during the rush hours, there often exist routing requests from multiple riders simultaneously, which has not been carefully investigated before. In this paper, we study the routing problem for multiple shared-bike riders with hardness analyses and approximation algorithms. The challenge lies in how to allocate the limited resources (bikes/docks at the stations) among the competing riders. We show that this problem is NP-hard, and thus propose two heuristics. We also propose an optimization technique on routing plan generations, to improve the efficiency of the algorithms. Extensive experiments have been carried out to verify the performance of the proposed algorithms. It turns out that the greedy-based routing algorithm, which has an approximation factor of 1/3, is both effective and efficient.

Geo-social groupqueries, which return a social cohesive user group with a spatial constraint, have receive significant research interests due to their promising applications for group-based activity planning and scheduling in location-based social networks (LBSNs). However, existing studies on geo-social group queries mostly assume the users are stationary whereas in realistic LBSN application scenarios all users may continuously move over time. Thus, in this paper, we investigate the problem ofcontinuousgeo-socialgroupsmonitoring(CGSGM) over moving users. A challenge in answering CGSGM queries over moving users is how to efficiently update geo-social groups when users are continuously moving. To address the CGSGM problem, we first propose a baseline algorithm, namelyBaseline-BB, which recomputes the new geo-social groups from scratch at each time instance by utilizing a branch and bound (BB) strategy. To improve the inefficiency of BB, we explore a new strategy, called common neighbor or neighbor expanding (CNNE), which expands the common neighbors of edges or the neighbors of users in intermediate groups to quickly produce the valid group combinations. Accordingly, another baseline algorithm, namelyBaseline-CNNE, is proposed. As these baseline algorithms do not maintain intermediate results to facilitate further query processing, we develop an incremental algorithm, calledincremental monitoring algorithm (IMA), which maintains the support, common neighbors and the neighbors of current users when exploring possible user groups for further updates and query processing. Since IMA requires many times of truss decomposition when processing mutiple-users updates, we propose an improved incremental algorithm, calledimproved incremental monitoring algorithm (IIMA), which performs truss decompostion only once. Moreover, we design algorithms for handling the social changes that result in insertion/deletion of some edges in the social network. Owing to the challenge in setting, an appropriate monitoring distance, we further study the top$N$CGSGM problem, which finds top$N$result groups at each time instance. Finally, we conduct extensive experiments using four real datasets to validate our ideas and evaluate the proposed algorithms.

In spite of its wide usage in various applications, existing construction methods for Knowledge Base (KB) are still on their way to obtaining 100% correct facts. Thus, employing crowd workers to validate a KB has been proposed to improve its reliability. Most of the existing works focus on devising games with proper incentives to engage workers in validating more facts, but rarely consider matching facts with proper workers. Facts have diverse domains (topics), which naturally require workers of different expertise. In addition, they also generally have different utilities, i.e., some are more heavily used than others. Thus, distinguishing the facts in terms of utility to give them different validation priorities is meaningful, especially when the budget is limited. To this end, we study the crowdsourced fact validation problem which considers worker domains and fact utilities, and find that with some reductions, it can be solved by the existing minimum cost network flow method. However, directly employing that method requires a huge time cost. We thereby propose an optimized network flow method which reduces the network complexity to save the time cost by properly grouping the facts. Furthermore, we propose an incremental validation method, which utilizes the previous results for validating an evolving KB. We finally conduct extensive experiments to demonstrate the effectiveness of the proposed methods.

Nowadays, ridesharing becomes a popular commuting mode. Dynamically arriving riders post their origins and destinations, then the platform assigns drivers to serve them. In ridesharing, different groups of riders can be served by one driver if their trips can share common routes. Recently, many ridesharing companies (e.g., Didi and Uber) further propose a new mode, namely "ridesharing with meeting points". Specifically, with a short walking distance but less payment, riders can be picked up and dropped off around their origins and destinations, respectively. In addition, meeting points enables more flexible routing for drivers, which can potentially improve the global profit of the system. In this paper, we first formally define the Meeting-Point-based Online Ridesharing Problem (MORP). We prove that MORP is NP-hard and there is no polynomial-time deterministic algorithm with a constant competitive ratio for it. We notice that a structure of vertex set, k -skip cover, fits well to the MORP. k -skip cover tends to find the vertices (meeting points) that are convenient for riders and drivers to come and go. With meeting points, MORP tends to serve more riders with these convenient vertices. Based on the idea, we introduce a convenience-based meeting point candidates selection algorithm. We further propose a hierarchical meeting-point oriented graph (HMPO graph), which ranks vertices for assignment effectiveness and constructs k -skip cover to accelerate the whole assignment process. Finally, we utilize the merits of k -skip cover points for ridesharing and propose a novel algorithm, namely SMDB, to solve MORP. Extensive experiments on real and synthetic datasets validate the effectiveness and efficiency of our algorithms.

In this paper, we study the privacy-preserving task assignment problem in spatial crowdsourcing, where the locations of both workers and tasks, prior to their release to the server, are perturbed with Geo-Indistinguishability (a differential privacy notion for location-based systems). Different from the previously studied online setting, where each task is assigned immediately upon arrival, we target the batch-based setting, where the server maximizes the number of successfully assigned tasks after a batch of tasks arrive. To achieve this goal, we propose the k-Switch solution, which first divides the workers into small groups based on the perturbed distance between workers/tasks, and then utilizes Homomorphic Encryption (HE) based secure computation to enhance the task assignment. Furthermore, we expedite HE-based computation by limiting the size of the small groups under k. Extensive experiments demonstrate that, in terms of the number of successfully assigned tasks, the k-Switch solution improves batch-based baselines by 5.9X and the existing online solution by 1.74X, with no privacy leak.

With the rapid development of smart mobile devices, the car-hailing platforms (e.g., Uber or Lyft) have attracted much attention from the academia and the industry. In this paper, we consider a dynamic car-hailing problem, namely maximum revenue vehicle dispatching (MRVD), in which rider requests dynamically arrive and drivers need to serve riders such that the entire revenue of the platform is maximized. We prove that the MRVD problem is NP-hard and intractable. To handle the MRVD problem, we propose a queueing-based vehicle dispatching framework, which first uses existing machine learning models to predict the future vehicle demand of each region, then estimates the idle time periods of drivers through a double-sided queueing model for each region. With the information of the predicted vehicle demands and estimated idle time periods of drivers, we propose two batch-based vehicle dispatching algorithms to efficiently assign suitable drivers to riders such that the expected overall revenue of the platform is maximized during each batch processing. Through extensive experiments, we demonstrate the efficiency and effectiveness of our proposed approaches over both real and synthetic datasets. In summary, our methods can achieve 3% ~ 10% increase on overall revenue without sacrificing on running speed compared with the state-of-the-art solutions.

As an important operator for spatial data analytics, Region of Interest (ROI) query is of great importance in many location-based services such as event detection, location recommendation and smart transportation. To address the challenge of conducting ROI queries on the increasingly complex spatial data, we present RIDE, an efficient and effective system for generalized ROI Discovery and Exploration. Different from existing studies and systems, RIDE supports a large spectrum of region score functions and query geometries, enabling customized ROI queries for different application scenarios. This demonstration proposal introduces the basic concept of ROI queries and key components of the RIDE system, including data storage and indexing, ROI query processing and optimization and user interface.

Recent years witnessed the emergence of various applications on knowledge graphs, which are often represented as RDF graphs. However, due to the lack of data schema and the complexity of SPARQL language, there is usually a gap between the user's real desire and the actual meaning of a SPARQL query, especially when the query itself is complicated. In this paper, we try to narrow this gap by modifying a given query with a set of modifiers, so that its result approaches a user-provided example set. Specifically, we model this problem as two individual sub-problems, query-restricting, and query-relaxing, both of which are shown to be NP-hard. We further prove that unless P=NP, query-restricting has no polynomial-time approximation scheme (PTAS), and query-relaxing has no polynomial-time constant-factor approximation algorithm. Despite their hardness, we propose a (1-1/ε)-approximation method for query-restricting and 2 heuristics for query-relaxing. Extensive experiments have been conducted on real-world knowledge graphs to evaluate the effectiveness and efficiency of our proposed solutions.

The dramatic development of shared mobility in food delivery, ridesharing, and crowdsourced parcel delivery has drawn great concerns. Specifically, shared mobility refers to transferring or delivering more than one passenger/package together when their traveling routes have common sub-routes or can be shared. A core problem for shared mobility is to plan a route for each driver to fulfill the requests arriving dynamically with given objectives. Previous studies greedily and incrementally insert each newly coming request to the most suitable worker with a minimum travel cost increase, which only considers the current situation and thus not optimal. In this paper, we propose a demand-aware route planning (DARP) for shared mobility services. Based on prediction, DARP tends to make optimal route planning with more information about requests in the future. We prove that the DARP problem is NP-hard, and further show that there is no polynomial-time deterministic algorithm with a constant competitive ratio for the DARP problem unless P=NP. Hence, we devise an approximation algorithm to realize the insertion operation for our goal. With the insertion algorithm, we devise a prediction based solution for the DARP problem. Extensive experiment results on real datasets validate the effectiveness and efficiency of our technique.

Recently, spatial crowdsourcing has been drawing increasing attention with its great potential in collecting geographical knowledge. The system throughput (number of assigned tasks) and workers' travel distance are two of many important factors in spatial crowdsourcing, and the improvement to one of them usually means the sacrifice of the other. However, most existing works resolve the trade-off between these two factors by simply targeting tasks within a bounding circle of each worker. In this paper, we compromise between the throughput and the distance by formulating these two factors as score terms in the objective function. This flexible formulation has the advantages of abandoning distant tasks and minimizing workers' travel distance for reachable tasks. Aside from that, we study the multi-campaign scenario of spatial crowdsourcing, which is not uncommon in practical applications while not yet discussed in existing works. The worker diversity of the campaigns is considered to be another goal and formulated as another score term in the objective function. Subsequently, the problem of multi-campaign oriented spatial crowdsourcing is to maximize the objective function comprised by the aforementioned score terms. We prove that the problem is NP-hard, thus, we propose several approximation solutions. Extensive experiments have been conducted to confirm the effectiveness and the efficiency of the devised solutions.

Ridesharing plays a more and more important role in modern transport. In this paper, we propose solutions for the bonus-offering scenario of ridesharing platforms (service providers). When vehicles are in shortage, requesters are allowed to offer bonus so that their orders can get prioritized in the dispatch process. To enable self-motivated bonus bidding of requesters, we devise an auction mechanism, where requesters are supposed to submit their bids truthfully and the platform conducts order dispatch and pricing. Our goal is to maximize the overall utility of the auction, while ensuring desirable auction properties such as truthfulness and individual rationality. To realize that, we propose a greedy and a ranking approach for order dispatch and their corresponding pricing strategies. Extensive experiments on real data suggest that the ranking approach is both effective and efficient.

The increasing popularity of crowdsourcing markets enables the application of crowdsourcing classification tasks. How to conduct quality control in such an application to achieve accurate classification results from noisy workers is an important and challenging task, and has drawn broad research interests. However, most existing works do not exploit the label acquisition phase, which results in their disability of making a proper budget allocation. Moreover, some works impractically make the assumption of managing workers, which is not supported by common crowdsourcing platforms such as AMT or CrowdFlower. To overcome these drawbacks, in this paper, we devise a Dynamic Label Acquisition and Answer Aggregation (DLTA) framework for crowdsourcing classification tasks. The framework proceeds in a sequence of rounds, adaptively conducting label inference and label acquisition. In each round, it analyzes the collected answers of previous rounds to perform proper budget allocation, and then issues the resultant query to the crowd. To support DLTA, we propose a generative model for the collection of labels, and correspondingly strategies for label inference and budget allocation. Experimental results show that compared with existing methods, DLTA obtains competitive accuracy in the binary case. Besides, its extended version, which plugs in the state-of-the-art inference technique, achieves the highest accuracy.

The system throughput and workers' travel distance are two important factors in spatial crowdsourcing and improving one of them usually means sacrificing the other. However, existing works either fail to consider the trade-off between these two factors or resolve their conflicts by simply targeting tasks within a bounding circle for each worker. In this paper, we compromise between the throughput and the distance by formulating these two factors as score terms in the objective function. Apart from that, we study the multi-campaign scenario in our problem, which is not uncommon in practical applications while not yet discussed in existing works. The worker diversity of the campaigns is formulated as another score term in the objective function. The problem of multi-campaign oriented spatial crowdsourcing is to maximize the aforementioned score function. We prove the problem is NP-hard and provide several approximation solutions. Extensive experiments have been conducted to validate the devised solutions.

With the prevalence of car-hailing applications, ridesharing becomes more and more popular because of its great potential in monetary saving and environmental protection. Order dispatch is the key problem in ridesharing, which has a strong impact on riders' experience and platform's performance. Existing order dispatch research works fail to consider the price of the orders, which can be an important reference because it directly relates to the platform's profit. Our work takes the order price into concern, and formulates a constrained optimization problem, which takes platform's profit as the optimization objective and performs controls on riders' detour distance and waiting time. We prove the problem is NP-hard, thus, we propose approximation methods. We further develop a simulation framework based on real ridesharing order and vehicle data. We conduct experiments with this simulation framework to evaluate the effectiveness and efficiency of the proposed methods.

With the rapid development of mobile networks and the widespread usage of mobile devices, spatial crowdsourcing [1], which outsources location-related tasks to moving workers, has drawn increasing attention. Spatial crowdsourcing differs from traditional crowdsourcing in that tasks released by a requester are location-related, and workers should physically travel to a specific spot to perform the task. Task assignment is an important issue in spatial crowdsourcing. Most existing works adopt SAT (Server Assigned Tasks) assignment mode [1], where the SC-server assigns tasks to workers in regular timestamps. However, existing works [1], [2], [3] on this mode are based on the assumption that no rejection would happen after the assignment and workers guarantee to perform their assigned tasks. In practice, a rejection would happen when the worker is not interested in the assigned tasks, which may result from long travel distance, critical time requirement, dissatisfactory payment, workers' lacking skills and etc. In the typical application of spatial crowdsourcing, Uber, workers (drivers) are allowed to reject the ride requests assigned by the server. Uber requires its drivers to accept at least 90 percent of the trip requests in order to avoid low system throughput and poor experience for riders [4]. Taking workers' rejections into concern, in spatial crowdsourcing, how to match the workers with the right tasks to maximize their acceptance is of great importance. Without consideration of workers' acceptance, the system's throughput cannot be guaranteed.

With the rapid development of mobile networks and the widespread usage of mobile devices, spatial crowdsourcing, which refers to assigning location-based tasks to moving workers, has drawn increasing attention. One of the important issues in spatial crowdsourcing is task assignment, which allocates tasks to appropriate workers. However, existing works generally assume that no rejection would happen after the task assignment is completed by the server. Ignorance of such an operation can lead to low system throughput. Thus, in this paper, we take workers' rejection into consideration and try to maximize workers' acceptance in order to improve the system throughput. Specifically, we first formally define the problem of maximizing workers' acceptance in rejection-aware spatial crowdsourcing. Unfortunately, the problem is NP-hard. We propose two exact solutions to obtain the optimal assignment, but they are not efficient enough and not scalable for large inputs. Then, we present four approximation approaches for improving the efficiency. Finally, we show the effectiveness of the proposed pruning strategy for the exact solutions and the superiority of the proposed Greedy algorithm over other approximation methods through extensive experiments.