Continuous k-Nearest Neighbour Strategies Using the mqrtree

Recently more and more people focus on continuous K-Nearest Neighbor (CKNN) query processing over moving Objects in Road Networks. A CKNN query is to find among all moving objects the K-nearest neighbors (KNNs) of a moving query object during a period of time. The main issue with existing methods is that moving objects change their locations frequently over time and if their location updates cannot be processed in time, the system runs the risk of retrieving the incorrect results of KNN. In this paper, an effective method is proposed to deal with continuous K-Nearest Neighbor query processing. By considering whether a moving object o is moving farther away from or getting closer to a query point q, the object which is definitely not in the KNN result set is effectively excluded. Thus we can reduce the communication cost, meanwhile we can also simplify the network distance computation between moving objects and query q. Comprehensive experiments are conducted and the results verify the effectiveness of the proposed algorithms.

One of the most important queries in spatio-temporal databases that aim at managing moving objects efficiently is the continuous K-nearest neighbor (CKNN) query. A CKNN query is to retrieve the K-nearest neighbors (KNNs) of a moving user at each time instant within a user-given time interval [t s , t e ]. In this paper, we investigate how to process a CKNN query efficiently. Different from the previous related works, our work relieves the past assumption, that an object moves with a fixed velocity, by allowing that the velocity of the object can vary within a known range. Due to the introduction of this uncertainty on the velocity of each object, processing a CKNN query becomes much more complicated. We will discuss the complications incurred by this uncertainty and propose a cost-effective P2 KNN algorithm to find the objects that could be the KNNs at each time instant within the given query time interval. Besides, a probability-based model is designed to quantify the possibility of each object being one of the KNNs. Comprehensive experiments demonstrate the efficiency and the effectiveness of the proposed approach.

Digital ecosystems are formed by “digital organisms” in complex, dynamic, and interrelated ecosystems and utilize multiple technologies to provide cost-efficient digital services and value-creating activities. A distributed wireless mobile network that serves as the underlying infrastructure to digital ecosystems provides important applications to the digital ecosystems, two of which are mobile navigation and continuous mobile information services. Most information and query services in a mobile environment are continuous mobile query processing or continuous k nearest neighbor (CKNN), which finds the locations where interest points or interest objects change while mobile users are moving. These locations are known as “split nodes.” All of the existing works on CKNN divide the query path into segments, which is a segment of road separated by two intersections, and then, the process to find split nodes is applied to each segment. Since there are many segments (due to many intersections, obviously), processing each segment is naturally inefficient. In this paper, we propose an alternative solution to overcome this problem. We use the Voronoi diagram for CKNN [called Voronoi CKNN (VCKNN)]. Our proposed approach does not need to divide the query path into segments, hence improving the overall query processing performance. Our experiment verified the applicability of the VCKNN approach to solve CKNN queries.

In this paper we propose a strategy for continuous k-nearest neighbour query processing for location-based services. Our approach applies clustering, which has not been applied to k-nearest neighbour processing by other works. Using a clustered point set on the server, a safe region is formed using a subset of the existing clusters. As long as the user's location (i.e., query point) remains in the safe region, the data set on the server can be used to accurately answer all k-nearest neighbour queries the majority of the time. Our strategy is an approximation strategy, as there are situations where the result produced for the user may not be accurate. However, an evaluation of our strategy show that the result is accurate at least 70% of the time in most cases. We also observed that when compared to repeated k-nearest neighbour search, our strategy is computationally significantly faster for a larger dataset. Therefore, it is worth the trade-off of less than 100% accuracy to achieve results quickly, and for several applications (e.g., restaurant searching), this can be ideal.

The use of Spatial Access Methods (SAMs) in spatial database systems, such as Geographical Information Systems, is necessary to achieve efficient retrieval of data items according to their spatial properties. Existing SAMs organizing minimum bounding rectangle (MBR) approximations of spatial objects can be classified into four groups. Each group is characterized by the special technique adopted for managing MBRs: (a) Ordering, (b) Transformation, (c) Clipping, and (d) Overlapping. This paper introduces a new technique. The basic idea of this technique is to represent all spatial objects by their MBRs and further reduce them into points of the same dimensionality, so that any multidimensional Point Access Method (PAM) may be used to support access. Essential for the functionality of the new method is the query window extension. The results of both analytical and experimental work show that SAMs using the new technique clearly outperform popular SAMs, such as the R- and R*-trees for data sets consisting of equal-sized MBRs. As for data sets of varying MBR sizes a competitive performance can be obtained.

The continuous K nearest neighbor (CKNN) query is an important type of query that finds continuously the KNN to a query point on a given path. We focus on moving queries issued on stationary objects in Spatial Network Database (SNDB) The result of this type of query is a set of intervals (defined by split points) and their corresponding KNNs. This means that the KNN of an object traveling on one interval of the path remains the same all through that interval, until it reaches a split point where its KNNs change. Existing methods for CKNN are based on Euclidean distances. In this paper we propose a new algorithm for answering CKNN in SNDB where the important measure for the shortest path is network distances rather than Euclidean distances. We propose DAR and eDAR algorithms to address CKNN queries based on the progressive incremental network expansion (PINE) technique. Our experiments show that the eDAR approach has better response time, and requires fewer shortest distance computations and KNN queries than approaches that are based on VN3 using IE.

In the real-time series streaming environments, such as data analysis in sensor networks, online stock analysis, video surveillance and weather forecasting, similarity search, which aims at retrieving the similarity between two or more streams, is a hot issue in the recent years. How to find continuous k-nearest neighbors (CKNN) queries has been one of the most common applications in computing on DSMS. In this paper, we developed traditional skylines technique and propose W-Skyline to process CKNN queries as a bandwidth efficient approach over distributed streams. It tries to use of wavelet transformations as a dimensionality reduction technique to permit efficient similarity search over time-series data in memory. Finally, we will give an extensive experimental study with real-time data sets that verifies the effectiveness of our W-Skyline transformation approach in similarity search and CKNN discovery within arbitrary ranges in the time series streaming environments.

In this paper, two new families of constructive self-organizing maps (SOMs), SAM-SOM* and MAM-SOM*, are proposed. These families are specially useful for information retrieval from large databases, high-dimensional spaces and complex distance functions which usually consume a long time. They are generated by incorporating spatial access method (SAM) and metric access method (MAM) into SOM with the maximum insertion rate, i.e. the case when a new unit is created for each pattern presented to the network. In this specific case, the network presents interesting advantages and acquires new properties which are quite different of traditional SOM. In a constructive SOM, if new units are rarely inserted into network, the training algorithm would probably need a long time to converge. On the other hand, if new units are inserted frequently, the training algorithm would not have enough time to adapt these units to the data distribution. Besides, training time is increased because the search for the winning neuron is traditionally performed sequentially. The use of SAM and MAM combined with SOM open the possibility of training constructive SOM with as much units as existing patterns with less time and interesting advantages compared with both models: Kohonen network SOM and SAMSOM model (SOM using SAM). Advantages and drawbacks of these new families are also discussed. These new families are useful to improve both SOM and SAM techniques.

<p>Due to the growth in mobile phones, the location based service (LBS) market is growing tremendously fast. Many mobile phone applications uses LBS such as store finder, car navigation system etc. LBS provide services to mobile users based on location & data profile of user’s hence users private information may get violated. In order to protect users private information many solutions are offered but most of them only addressed on snapshot query and no support for continual query and Moving Query Moving Object(MQMO).</p> <p><a href="https://journalnx.com/journal-article/20150568">https://journalnx.com/journal-article/20150568</a></p>

Direct neighbor search

Continuous queries for moving objects are becoming more and more important due to the increasing number of application domains that deal with moving entities. The asynchronous updating algorithm for continuous queries of moving objects is superior to synchronous updating algorithms in communication cost. By improving Haibo Hu's rectangle safe region strategy we proposed a new continuous queries algorithm. Circle safe region and dynamic interval are adopted in our algorithm. Theory proof and experiment results show that our algorithm substantially outperforms the traditional periodic monitoring and the rectangle safe region algorithms in terms of monitoring accuracy, communication cost and CPU time. Furthermore, the mobile terminals need not have any computation ability in our algorithm

We present a technique to decluster a spatial access method on a shared-nothing multi-computer architecture [DGS+90]. We propose a software architecture with the R-tree as the underlying spatial access method, with its non-leaf levels on the ‘master-server’ and its leaf nodes distributed across the servers. The major contribution of our work is the study of the optimal capacity of leaf nodes, or ‘chunk size’ (or ‘striping unit’): we express the response time on range queries as a function of the ‘chunk size’, and we show how to optimize it.

This paper presents an evaluation of the mqr-tree for indexing a database containing a very large number of objects. Many spatial access methods have been proposed for handling either point and/or region data, with the vast majority able to handle a limited number of instances of these data types efficiently. However, many established and emerging application areas, such as recommender systems, require the management and indexing of very large object sets, such as a million places of interest that are each represented with a point. Using between one and five million points and objects, a comparison of both index construction and spatial query evaluation is performed versus a benchmark spatial indexing strategy. We show that the mqr-tree achieves significantly lower overlap and overcoverage when used to index a very large collection of objects. Also, the mqr-tree achieves significantly improved query processing performance in many cases. Therefore, the mqr-tree is a significant candidate for handling very large object sets for emerging applications.

The increasing demand for the use of database systems as an integrating factor in CAD/CAM applications has necessitated the development of database systems with appropriate modelling and retrieval capabilities. One essential problem is the treatment of geometric data which has led to the development of spatial databases. Unfortunately, most proposals only deal with simple geometric objects like multidimensional points and rectangles. On the other hand, there has been a rapid development in the field of representing geometric objects with free form curves or surfaces, initiated by engineering applications such as mechanical engineering, aviation or astronautics. Therefore, we propose a concept for the realization of spatial retrieval operations on geometric objects with free form boundaries, such as B-spline or Bezier curves, which can easily be integrated in a database management system. The key concept is the encapsulation of geometric operations in a so-called query processor. First, this enables the definition of an interface allowing the integration into the data model and the definition of the query language of a database system for complex objects. Second, the approach allows the use of an arbitrary representation of the geometric objects. After a short description of the query processor, we propose some representations for free form objects determined by B-spline or Bezier curves. The goal of efficient query processing in a database environment is achieved using a combination of decomposition techniques and spatial access methods. Finally, we present some experimental results indicating that the performance of decomposition techniques is clearly superior to traditional query processing strategies for geometric objects with free form boundaries.

This work investigates the performance of several spatial access methods with respect to the distribution of the indexed spatial objects. Although having gathered storage and insertion costs as well this work focuses on some issues regarding query costs. The performance results have showed that the R/sup +/-tree was the best spatial index structure for the point queries and the enclosure range queries, whereas the R/sup */-trees have produced the best outcomes for the intersection and the containment range queries. The Hilbert R-tree and the SR-tree have generated low performance results for any investigated query type. However, additional performance tests have showed that a variation in both the size and the shape properties of the data rectangles provided competitive results for the Hilbert R-tree and the SR-tree, mainly for the intersection and the containment queries.