235091
Efficient detection of empty-result queries
Frequently encountered in query processing, empty query results usually do not provide users with much useful information. Yet, users might still have to wait for a long time before they disappointingly realize that their results are empty. To significantly reduce such unfavorable delays, in this paper, we propose a novel method to quickly detect, without actual execution, those queries that will return empty results. Our key idea is to remember and reuse the results from previously-executed, empty-result queries. These results are stored in the form of so-called atomic query parts so that the (partial) results from multiple queries can be combined together to handle a new query without incurring much overhead. To increase our chance of detecting empty-result queries with only a limited storage, our method (1) stores the most "valuable" information about empty-result queries, (2) removes redundant information among different empty-result queries, (3) continuously updates the stored information to adapt to the current query pattern, and (4) utilizes a set of special properties of empty results. We evaluate the efficiency of our method through a theoretical analysis and an initial implementation in PostgreSQL. The results show that our method has low overhead and can often successfully avoid executing empty-result queries.
10289907
Partial Materialized Views
Early access to partial query results is highly desirable during exploration of massive data sets. However, it is challenging to provide transactionally consistent, immediate partial results without significantly increasing queries' execution time. To address this problem, this paper proposes a partial materialized view (PMV) method to cache some of the most frequently accessed results rather than all the possible results. Compared to traditional materialized views, the proposed PMVs do not require maintenance during insertion into base relations, and have much smaller storage and maintenance overhead. Upon the arrival of a query, the RDBMS first searches the PMV and returns to the user the cached partial results. Since a large portion of the PMV is cached in memory, this usually finishes within a millisecond. Then the RDBMS continues to execute the query to find the remaining results. The efficiency of our PMV method is evaluated through a simulation study, a theoretical analysis, and an initial implementation in PostgreSQL.
2438435
Real-time new event detection for video streams
Online detection of video clips that present previously unseen events in a video stream is still an open challenge to date. For this online new event detection (ONED) task, existing studies mainly focus on optimizing the detection accuracy instead of the detection efficiency. As a result, it is difficult for existing systems to detect new events in real time, especially for large-scale video collections such as the video content available on the Web. In this paper, we propose several scalable techniques to improve the video processing speed of a baseline ONED system by orders of magnitude without sacrificing much detection accuracy. First, we use text features alone to filter out most of the non-new-event clips and to skip those expensive but unnecessary steps including image feature extraction and image similarity computation. Second, we use a combination of indexing and compression methods to speed up text processing. We implemented a prototype of our optimized ONED system on top of IBM's System S. The effectiveness of our techniques is evaluated on the standard TRECVID 2005 benchmark, which demonstrates that our techniques can achieve a 480-fold speedup with detection accuracy degraded less than 5%.
379901
Answering linear optimization queries with an approximate stream index
We propose a SAO index to approximately answer arbitrary linear optimization queries in a sliding window of a data stream. It uses limited memory to maintain the most “important” tuples. At any time, for any linear optimization query, we can retrieve the approximate top-K tuples in the sliding window almost instantly. The larger the amount of available memory, the better the quality of the answers is. More importantly, for a given amount of memory, the quality of the answers can be further improved by dynamically allocating a larger portion of the memory to the outer layers of the SAO index.
6802163
Transaction reordering with application to synchronized scans
Traditional workload management methods mainly focus on the current system status while information about the interaction between queued and running transactions is largely ignored. An exception to this is the transaction reordering method, which reorders the transaction sequence submitted to the RDBMS and improves the transaction throughput by considering both the current system status and information about the interaction between queued and running transactions. The existing transaction reordering method only considers the reordering opportunities provided by analyzing the lock conflict information among multiple transactions. This significantly limits the applicability of the transaction reordering method. In this paper, we extend the existing transaction reordering method into a general transaction reordering framework that can incorporate various factors as the reordering criteria. We show that by analyzing the resource utilization information of transactions, the transaction reordering method can also improve the system throughput by increasing the resource sharing opportunities among multiple transactions. We provide a concrete example on synchronized scans and demonstrate the advantages of our method through experiments with a commercial parallel RDBMS.
44490004
Fault Models in Testing
1980102
Dynamic Rate Assignment and Power Control in Uplink UMTSW-CDMA Systems
Power control and rate assignment are important tools to maximize system resource utilization while satisfying quality of service (QoS) in a code division multiple access (CDMA) system. In this paper, we propose an algorithm of simultaneously adapting transmission power and data rate to maximize system throughput and minimize the power consumption in a wideband CDMA (W-CDMA) network. The greedy rate packing (GRP) allocation scheme, where high date rates are assigned to users with favorite channel conditions and lower interference, is employed for the rate adaptation. Compared with the results using Zhao et al. (2005) (algorithm 2), close-loop power control (CLPC) alone, and rate adaptation alone approaches, our proposed power and rate transmission scheme (algorithm 1) significantly improves transmission efficiency
15224900
A Novel Clock Duty-Cycle Corrector of DSP Systems
A novel 50% duty-cycle corrector (DCC) of digital signal processing (DSP) systems, designed with a purely digital phase-blending technique, is presented in this paper. The novel features of the proposed DCC includes a higher reliability against process, voltage and temperature variation due to the use of the synchronous mirror delay (SMD) technique, no-skew output clock, and a much faster duty-cycle correction speed compared to conventional DCC's. When designed with a 0.13-μm CMOS technology, the acceptable duty-cycle of the input signal ranges from 10% to 90% when the clock frequency is 400 MHz and the correction operation spends 4 clock cycles with the corrected duty-cycle varying from 48% to 52%.
22377735
Failure-Equivalent Transformation of Transition Systems to Avoid Internal Actions
Abstract Labelled transition systems are often used as a theoretical framework for modelling communication protocols or distributed software systems. In order to model the deadlock properties of the systems, the internal transitions of the submodules are often represented globally by so-called internal actions. However, certain verification and testing methods assume that the specification of the system is given in the form of a transition system without internal actions. This paper shows that most labelled transition systems with internal actions can be transformed into a failure-equivalent labelled transition system without internal actions. A sufficient condition is given, and an algorithm is described which does the transformation for any transition system which satisfies the condition. This algorithm can be applied to use the above verification and testing methods also for specification including internal actions.
30097914
Improved Method for Network Danger Evaluation Based on Immunology Principle
This paper proposes an improved immunological surveillance for network danger evaluation model, focusing on intrusion detection and countermeasures with respect to widely-used networks. An improved intrusion detection mechanism based on self-tolerance, clone selection, and immune surveillance is established. A new network security evaluation method using antibody concentration to quantitatively analyze the degree of intrusion danger level is presented. Additionally, this new hierarchical management framework of the proposed model adopt to improve the detection efficiency and to overcome the shortcoming of the local optimum. The experimental results show that the proposed model is a good solution for network security evaluation.