In this paper, an interval-gap-based 1NF temporal tuple calculus language and the corresponding temporal relation algebra are established on the basis of considering the trouble of stack operations in both S. Gadia’s...In this paper, an interval-gap-based 1NF temporal tuple calculus language and the corresponding temporal relation algebra are established on the basis of considering the trouble of stack operations in both S. Gadia’s TCAL and temporal tuple calculus due to their NINF.展开更多
A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to fur...A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.展开更多
Real-time database systems contain not only transaction timing constraints, but also data timing constraints. This paper discusses the temporal characteristics of data in real-time databases and offers a definition of...Real-time database systems contain not only transaction timing constraints, but also data timing constraints. This paper discusses the temporal characteristics of data in real-time databases and offers a definition of absolute and relative temporal consistency. In real-time database systems, it is often the case that the policies of transaction schedules only consider the deadline of real-time transactions, making it insufficient to ensure temporal correctness of transactions. A policy is given by considering both the deadlines of transactions and the “data deadline” to schedule real-time transactions. A real-time relational data model and a real-time relational algebra based on the characteristics of temporal data are also proposed. In this model, the temporal data has not only corresponding values, but also validity intervals corresponding to the data values. At the same time, this model is able to keep historical data values. When validity interval of a relation is [NOW, NOW], real-time relational algebra will transform to traditional relational algebra.展开更多
With the development of wireless communications and positioning technologies, tracking the positions of moving objects has increased necessary. This paper proposes a Cache-Conscious TPR -Link tree called CTPR Link tre...With the development of wireless communications and positioning technologies, tracking the positions of moving objects has increased necessary. This paper proposes a Cache-Conscious TPR -Link tree called CTPR Link tree which store in main memory. To satisfy continuous movement, the QRMBR definition is modified. The compression leads to the reduction of the tree height, which improves the cache behavior of the index and reduces the memory access time. In order to achieve high concurrency control, optimistic dynamic versioning and sibling-link scheme is presented, which not only enable read-only transactions not to fail with latch-free but also reduce cache misses during index updates.展开更多
随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数...随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数据通常是不完整或带有噪声的,要求预测算法必须能够适应不完全的轨迹信息。基于此,提出了一种基于时空数据库的实时启发式轨迹预测模型(Real-time Heuristic Trajectory Prediction Based on Spatio-Temporal Databases,RHTP-STD)。RHTP-STD利用MobilityDB数据库平台存储和管理轨迹数据,通过图构建算法将轨迹数据转换为时空图。RHTP-STD采用启发式算法,融合历史和实时数据,快速预测移动对象的未来轨迹。实验结果表明,RHTP-STD在Argoverse数据集上的预测准确性和实时性均优于现有方法。讨论所提方法在不同应用场景中的适用性,提出了未来的研究方向。展开更多
This research takes the view that the modelling of temporal data is a fundamental step towards the solution of capturing semantics of time. The problemsinhereat in the mod6iling of time are not unique to datahase proc...This research takes the view that the modelling of temporal data is a fundamental step towards the solution of capturing semantics of time. The problemsinhereat in the mod6iling of time are not unique to datahase processing. Therepresentation of temporal knowledge and temporal reasoning arises in a widerange of other disciplines. ln this paper an account is given of a techniquefor modelling the semantics of temporal data and its associated normalizationmcthod. It discusses the techniques of processing temporal data by employinga Time Sequence (TS) data model. It shows a number of different strategieswhich are used to classify different data properties of temporal data, and it goeson.to develop the model of temporal data and addresses issues of temporal dataapplication design by introducing the concept of temporal data normalisation.展开更多
基金Supported by both the High Technology Research Development Programme of Chinathe National Natural Science Foundation of China
文摘In this paper, an interval-gap-based 1NF temporal tuple calculus language and the corresponding temporal relation algebra are established on the basis of considering the trouble of stack operations in both S. Gadia’s TCAL and temporal tuple calculus due to their NINF.
基金Project(60873030) supported by the National Natural Science Foundation of China
文摘A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.
基金Project 60073045 supported by National Natural Science Foundation of China
文摘Real-time database systems contain not only transaction timing constraints, but also data timing constraints. This paper discusses the temporal characteristics of data in real-time databases and offers a definition of absolute and relative temporal consistency. In real-time database systems, it is often the case that the policies of transaction schedules only consider the deadline of real-time transactions, making it insufficient to ensure temporal correctness of transactions. A policy is given by considering both the deadlines of transactions and the “data deadline” to schedule real-time transactions. A real-time relational data model and a real-time relational algebra based on the characteristics of temporal data are also proposed. In this model, the temporal data has not only corresponding values, but also validity intervals corresponding to the data values. At the same time, this model is able to keep historical data values. When validity interval of a relation is [NOW, NOW], real-time relational algebra will transform to traditional relational algebra.
基金This workis supported by Ministry of Information and Communication( MIC) Korea,under the Information Technology Research Center(ITRC) +1 种基金sup-port programsupervised by the Institute of Informationtechnology Assessment(IITA) Sino-Korea GIS Research Center ,China.
文摘With the development of wireless communications and positioning technologies, tracking the positions of moving objects has increased necessary. This paper proposes a Cache-Conscious TPR -Link tree called CTPR Link tree which store in main memory. To satisfy continuous movement, the QRMBR definition is modified. The compression leads to the reduction of the tree height, which improves the cache behavior of the index and reduces the memory access time. In order to achieve high concurrency control, optimistic dynamic versioning and sibling-link scheme is presented, which not only enable read-only transactions not to fail with latch-free but also reduce cache misses during index updates.
文摘随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数据通常是不完整或带有噪声的,要求预测算法必须能够适应不完全的轨迹信息。基于此,提出了一种基于时空数据库的实时启发式轨迹预测模型(Real-time Heuristic Trajectory Prediction Based on Spatio-Temporal Databases,RHTP-STD)。RHTP-STD利用MobilityDB数据库平台存储和管理轨迹数据,通过图构建算法将轨迹数据转换为时空图。RHTP-STD采用启发式算法,融合历史和实时数据,快速预测移动对象的未来轨迹。实验结果表明,RHTP-STD在Argoverse数据集上的预测准确性和实时性均优于现有方法。讨论所提方法在不同应用场景中的适用性,提出了未来的研究方向。
文摘This research takes the view that the modelling of temporal data is a fundamental step towards the solution of capturing semantics of time. The problemsinhereat in the mod6iling of time are not unique to datahase processing. Therepresentation of temporal knowledge and temporal reasoning arises in a widerange of other disciplines. ln this paper an account is given of a techniquefor modelling the semantics of temporal data and its associated normalizationmcthod. It discusses the techniques of processing temporal data by employinga Time Sequence (TS) data model. It shows a number of different strategieswhich are used to classify different data properties of temporal data, and it goeson.to develop the model of temporal data and addresses issues of temporal dataapplication design by introducing the concept of temporal data normalisation.
