Spatial Query Processing Algorithms Research Articles

DIM: a distributed air index based on MapReduce for spatial query processing in road networks

In this era of mobile application and socialization, location-based services (LBSs) have become unprecedentedly popular and emphasized. By submitting its location to the service provider, the mobile terminal can obtain useful service. As an important technology that can provide location-based services, spatial query processing has become a research hotspot. According to the problems existing in current road network partitioning, first of all, this paper proposes the partition density formula and the optimal road network partitioning method according to the partition density. Based on that, we propose the concepts of partition self-attraction, mutual attraction, and merger factor of partition to effectively merge the partitions with low densities, which can further reduce the number of unnecessary broadcast frames and optimize the index method. Then, we propose the real distributed air index method DIM and kNN spatial query processing algorithm based on the MapReduce platform. According to the DIM index method, the Name Node only stores the prime index, while not storing the data, and each frame consists of defined index and the data in a partition that need to be broadcasted. The mobile user can quickly localize the frame data that they need to obtain according to the main index or the index of current frame, in this way to reduce the tuning time and access latency, which can significantly optimize the query efficiency. Massive experiments have proved the stability and effectiveness of the proposed algorithm.

Efficient Computation of the Optimal Accessible Location for a Group of Mobile Agents

Nowadays, people can access location-based services (LBSs) as a group via mobile devices to plan their daily activities with friends and relatives. In this article, we introduce an important class of group-oriented LBSs, group optimal accessible location (GOAL) queries that enable users to identify the location of a point of interest (POI) that has the minimum total distance to a given set of paths. GOAL queries have many applications, such as the selection of an optimal location for group meet-ups or for a mobile facility such as a food truck. In a GOAL query, each trip or path is represented as a set of line segments, and the distance of a POI from a path is computed as the minimum distance of the POI to any line segment of the path. We develop an efficient approach to evaluate GOAL queries. The novelty of our GOAL query processing algorithm in contrast to other spatial query processing algorithms is the reformulation of a GOAL query by considering only a subset of path segments from the given set of paths, which is also the key factor behind the efficiency of our proposed algorithm. We exploit geometric properties and develop pruning techniques to eliminate both POIs and path segments that cannot provide the optimal solution for a GOAL query. Our experimental results demonstrate that we provide a readily deployable solution for real-life applications.

Elastic Spatial Query Processing in OpenStack Cloud Computing Environment for Time-Constraint Data Analysis

Geospatial big data analysis (GBDA) is extremely significant for time-constraint applications such as disaster response. However, the time-constraint analysis is not yet a trivial task in the cloud computing environment. Spatial query processing (SQP) is typical computation-intensive and indispensable for GBDA, and the spatial range query, join query, and the nearest neighbor query algorithms are not scalable without using MapReduce-liked frameworks. Parallel SQP algorithms (PSQPAs) are trapped in screw-processing, which is a known issue in Geoscience. To satisfy time-constrained GBDA, we propose an elastic SQP approach in this paper. First, Spark is used to implement PSQPAs. Second, Kubernetes-managed Core Operation System (CoreOS) clusters provide self-healing Docker containers for running Spark clusters in the cloud. Spark-based PSQPAs are submitted to Docker containers, where Spark master instances reside. Finally, the horizontal pod auto-scaler (HPA) would scale-out and scale-in Docker containers for supporting on-demand computing resources. Combined with an auto-scaling group of virtual instances, HPA helps to find each of the five nearest neighbors for 46,139,532 query objects from 834,158 spatial data objects in less than 300 s. The experiments conducted on an OpenStack cloud demonstrate that auto-scaling containers can satisfy time-constraint GBDA in clouds.

An efficient spatial query processing algorithm in multi-sink wireless sensor networks

In order to address the problem of energy and time-efficient execution of spatial queries in multi-sink wireless sensor networks, an efficient hybrid spatial query processing algorithm (EHSQP) is proposed in this paper. In EHSQP, sink nodes perform the sector selection for the query region and seek the query route to a query region using the known infrastructure information. Sensor nodes can adjust the query dissemination and reversing route for query results based on the available local information. To minimise the energy consumption and the response time, the proposed EHSQP algorithm ensures that only the relevant nodes are involved in the query execution. Experimental results show that the proposed algorithm reduces communication cost significantly, and saves energy and time very effectively for the connected sensors in the given region. The proposed technique has an advantage over other techniques in terms of energy and time-efficient query cover with lower communication cost.

An efficient spatial query processing algorithm in multi-sink wireless sensor networks

In order to address the problem of energy and time-efficient execution of spatial queries in multi-sink wireless sensor networks, an efficient hybrid spatial query processing algorithm EHSQP is proposed in this paper. In EHSQP, sink nodes perform the sector selection for the query region and seek the query route to a query region using the known infrastructure information. Sensor nodes can adjust the query dissemination and reversing route for query results based on the available local information. To minimise the energy consumption and the response time, the proposed EHSQP algorithm ensures that only the relevant nodes are involved in the query execution. Experimental results show that the proposed algorithm reduces communication cost significantly, and saves energy and time very effectively for the connected sensors in the given region. The proposed technique has an advantage over other techniques in terms of energy and time-efficient query cover with lower communication cost.

지오센서 네트워크의 다중 공간질의 최적화를 위한 공간질의처리비용 예측 알고리즘 연구

최근 IoT (Internet of Things) 기술의 발전과 더불어 무선 환경에서 특정 영역에 위치하는 센서노드의 위치-센서정보를 에너지 효율적으로 수집하는 센서 네트워크 기반 공간질의처리에 대한 관심이 크게 증가하고 있다. 그리하여 센서노드에서 공간 필터링을 직접 수행하여 센서노드들 간의 통신 횟수를 감소시켜 에너지 소모를 최소화하는 다양한 공간질의처리 알고리즘 및 분산 공간색인방법들이 제안되어 왔다. 그러나 단일 공간질의처리 최적화에 중점을 두었던 기존 공간색인방법 및 알고리즘들은 IoT 환경에서 다수 사용자에 의하여 요청되는 다중 공간질의를 최적화하여 수행하기에는 한계가 있었다. 이에 본 논문에서는 센서 네트워크에서 다중 공간질의를 에너지 효율적으로 처리할 수 있는 최적화 알고리즘을 제안하고 있다. 제안된 다중 공간질의 최적화 알고리즘은 인접 영역에 주어지는 공간질의들을 통합하여 수행하는 '질의통합' 개념을 기본으로 하고 있다. 최적화 과정에서 질의들의 통합 또는 개별 수행에 대한 판단은 각 수행비용을 예측하여 결정하며, 본 논문에서는 질의처리 비용 예측 방법을 추가적으로 제안하고 있다. 끝으로, 성능평가에서는 GR-tree, SPIX, CPS의 공간색인방법에 대한 비교 실험을 통하여 제안된 알고리즘의 성능 분석결과를 제시하고 있다. W ith the recent advancement of IoT (Internet of Things) technology, there has been much interest in the spatial query processing which energy-efficiently acquires sensor readings from sensor nodes inside specified geographical area of interests. Therefore, various kinds of spatial query processing algorithms and distributed spatial indexing methods have been proposed. They can minimize energy consumption of sensor nodes by reducing wireless communication among them using in-network spatial filtering technology. However, they cannot optimize multiple spatial queries which w ill be w idely used in IoT, because most of them have focused on a single spatial query optimization. Therefore, we propose a new multiple spatial query optimization algorithm which can energy-efficiently process multiple spatial queries in a sensor network. The algorithm uses a concept of 'query merging' that performs the merged set after merging multiple spatial queries located at adjacent area. Here, our algorithm makes a decision on which is better between the merged and the separate execution of queries. For such the decision making, we additionally propose the cost estimation method on the spatial query execution. Finally, we analyze and clarify our algorithm's distinguished features using the spatial indexing methods of GR-tree, SPIX, CPS.

Location-Based Data Dissemination for Spatial Queries in Wireless Broadcast Environments

Most current research on Location-Based Services (LBSs, for short) assumes point-to-point wireless communication, where the server processes a query and returns the query result to the user via a point-to-point wireless channel. However, LBSs via point-to-point wireless channel suffer from a tremendous amount of traffic and service requests from the user and thereby result in poor performance. In this paper, we present broadcast-based spatial query processing algorithms designed to support k-NN (k-Nearest Neighbor) and range queries via a wireless network. The task of the query processor is to selectively monitor the wireless broadcast channel, when the data items are disseminated by the server, according to their locations. Experiments are conducted to evaluate the performance of the proposed algorithms. Comprehensive experiments illustrate that the presented algorithms are highly scalable and are more efficient than the previous techniques in terms of both access time and energy consumption.

Hybrid Spatial Query Processing between a Server and a Wireless Sensor Network

There has been much interest in a spatial query which acquires sensor readings from sensor nodes inside specified geographical area of interests. A centralized approach performs the spatial query at a server after acquiring all sensor readings. However, it incurs high wireless transmission cost in accessing all sensor nodes. Therefore, various in-network spatial search methods have been proposed, which focus on reducing the wireless transmission cost. However, the in-network methods sometimes incur unnecessary wireless transmissions because of dead space, which is spatially indexed but does not contain real data. In this paper, we propose a hybrid spatial query processing algorithm which removes the unnecessary wireless transmissions. The main idea of the hybrid algorithm is to find results of a spatial query at a server in advance and use the results in removing the unnecessary wireless transmissions at a sensor network. We compare the in-network method through several experiments and clarify our algorithm's remarkable features.

A scalable energy-efficient continuous nearest neighbor search in wireless broadcast systems

When the mobile environment consists of light-weight devices, the energy consumption of location-based services (LBSs) and the limited bandwidth of the wireless network become important issues. Motivated by this, we propose new spatial query processing algorithms to support Mobile Continuous Nearest Neighbor Query (MCNNQ) in wireless broadcast environments. Our solution provides a general client---server architecture for answering MCNNQ on objects with unknown, and possibly variable, movement types. Our solution enables the application of spatio-temporal access methods specifically designed for a particular type, to arbitrary movements without any false misses. Our algorithm does not require any conventional spatial index for MCNNQ processing. It can be adapted to static or moving objects, and does not require additional knowledge (e.g., direction of moving objects) beyond the maximum speed and the location of each object. Extensive experiments demonstrate that our location-based data dissemination algorithm significantly outperforms index-based solutions.

Transform-space view: performing spatial join in the transform space using original-space indexes

Spatial joins find all pairs of objects that satisfy a given spatial relationship. In spatial joins using indexes, original-space indexes such as the R-tree are widely used. An original-space index is the one that indexes objects as represented in the original space. Since original-space indexes deal with extents of objects, it is relatively complex to optimize join algorithms using these indexes. On the other hand, transform-space indexes, which transform objects in the original space into points in the transform space and index them, deal only with points but no extents. Thus, optimization of join algorithms using these indexes can be relatively simple. However, the disadvantage of these join algorithms is that they cannot be applied to original-space indexes such as the R-tree. In this paper, we present a novel mechanism for achieving the best of these two types of algorithms. Specifically, we propose the new notion of the transform-space and present the transform-space join algorithm. The transform-space is a virtual transform-space index based on an original-space index. It allows us to interpret or view an existing original-space index as a transform-space index with no space and negligible time overhead and without actually modifying the structure of the original-space index or changing object representation. The transform-space join algorithm joins two original-space indexes in the transform space through the notion of the transform-space view. Through analysis and experiments, we verify the excellence of the transform-space join algorithm. The transform-space join algorithm always outperforms existing ones for all the data sets tested in terms of all three measures used: the one-pass buffer size (the minimum buffer size required for guaranteeing one disk access per page), the number of disk accesses for a given buffer size, and the wall clock time. Thus, it constitutes a lower-bound algorithm. We believe that the proposed transform-space can be applied to developing various new spatial query processing algorithms in the transform space.