23745663
A filtering method for searching similar multidimensional sequences under the time-warping distance
The filtering method is currently the most suitable approach for the fast retrieval of similar sequences under the time-warping distance. Several filtering methods under the time-warping distance have been proposed, but they are only for real number sequences. This paper presents an efficient filtering method for the retrieval of similar multidimensional sequences. First, we propose three basic filtering measures (the end-point distance, the min-region distance, and the interim time-warping distance) based on the ones appeared in the literature, and one of their direct combinations (the point-region distance). Next, we investigate their problems with a large number of multidimensional sequences. In order to alleviate those problems, we extend the end-point distance and the min-region distance into the extended end-point distance and the segmented min-region distance, respectively, and combine them into a novel measure, the extended point-region distance. A multi-step architecture is adopted to implement the retrieval process with the proposed measure. Experiments with synthetic sequences are conducted for the performance comparison.
14456420
A replica control method for improving availability for read-only transactions
Data replication is often considered in distributed database systems to enhance availability and performance. The benefit of data replication, however can only be realized at the cost of maintaining the consistency of data. In particular, network partition failures make it more difficult to achieve high data availability while ensuring strong correctness criteria such as l-copy serializability. We propose a replica control method to improve the availability of data in the presence of network partition failures. Our method extends the traditional primary copy method by using the relaxed correctness criterion called insular consistency for large-scale distributed systems, where partition failures frequently occur. We focus on increasing the availability of data for read-only transactions. We introduce a version vector as a tool for guaranteeing insular consistency and present a mechanism that allows read-only transactions to be executed at any partition as long as the insular consistency is satisfied. An asynchronous update propagation mechanism is also employed to improve the performance of update operations. We also show that the proposed method is correct and give some performance considerations.
37385528
A framework for handling dependencies among web services transactions
This paper proposes an effective Web services (WS) transaction management framework to automatically manage inconsistencies occurred by relaxing isolation of WS transactions.
38239153
Qualitative Behavior Modeling of Information Processing Components
This paper presents qualitative behavior modeling of Information Processing Components(IPCs), which are domain-specific software components for modeling reusable functions in database management systems(DBMSs). After introducing a detailed formal syntax of IPCs, we propose their modular, qualitative behavior generation mechanism. The proposed mechanism is based on qualitative modeling and simulation, thus produces a sequence of temporal state transitions of modeled IPCs. The proposed modeling mechanism aims to facilitate the scientific measurement of
591216
The HS File: A New Dynamic Signature File Method for Efficient Information Retrieval
Many works on the signature file methods have been made in the past, but they are mainly for static environments. However, many recent applications in practice require a dynamic information storage structure that effectively supports insertions, deletions and updates. Though there are a few signature file techiniques for dynamic environments, they suffer from serious performance degradation when query signature weights are light. In this paper, we propose a new dynamic signature file organization, called the hierarchical signature(HS) file, that solves the problem of light query signature weights. We perform simulation experiments by using wide range of parameter values. We show through performance comparison based on experiments that the HS file improves performance significantly in both the retrieval time and the storage over-head over the other dynamic signature file methods proposed earlier.
8831551
A per-object based hybrid concurrency control
Existing concurrency control algorithms do not conform well to various environments in the performance perspective. Each algorithm has some assumption on the conflict characteristic of its execution environment, and its performance degrades when the assumption fails. A per-object hybrid scheme integrating a two phase locking algorithm with a parallel validation technique is presented to solve this problem. Read and write accesses on each database object are controlled by one algorithm at a time. This controlling algorithm can alter while transactions are running, in order to enhance the overall system performance. In the simulation study, the proposed scheme with the proposed algorithm alteration strategy is shown to conform well to various execution environments, better than both the two phase locking algorithm and the parallel validation technique.
26477941
A novel direction-finding method for cyclostationary signals
We develop a method based on the phase-SCORE algorithm of Agee et al. (Proc. IEEE 78 (April 1990) 753) to achieve direction finding for cyclostationary signals. Using the weight obtained from the phase-SCORE algorithm, we construct a subspace orthogonal to the subspace spanned by the direction vectors of uncorrelated signals of interest (SOIs). Finding the directions of the uncorrelated SOIs is then performed according to a subspace-fitting concept. For coping with the coherence between SOIs, we incorporate the proposed method with the well-known spatial smoothing algorithm of Shan et al. (IEEE Trans. Acoust. Speech Signal Process ASSP-33 (August 1985) 806) to alleviate the performance degradation due to coherence. Simulation examples for illustration and comparison are also provided.
12876856
Virtual cell in mobile computer communications
In this paper, we design and develop a virtual cell approach for the transmission of IP datagrams in mobile computer communications. A virtual cell consists of a group of physical cells whose base stations are implemented by remote bridges and interconnected via high-speed datagram packet-switched networks. Host mobility is supported at the data link layer by virtual cell protocol (VCP) using the distributed hierarchical location information of mobile hosts. As far as the IP layer is concerned, it appears within a virtual cell as if the communication between two mobile hosts in different physical cells were taking place directly as in the same physical cell. Between virtual cells, a one-hop forwarding pointer from a mobile host's native virtual cell to its current virtual cell is maintained at the VCP layer. This means that the combination of the existing routing protocols of the IP layer and the forwarding pointer maintained at the VCP layer between virtual cells gives the same effect of having a fully duplicated location information among virtual cells for the global mobile network. Thus, the virtual cell approach eliminates the necessity of IP-level mobile host protocols that may interfere with the conventional IP protocol in a practical sense. In addition, given mobility and communication patterns among physical cells, it achieves a logically flexible coverage area of a virtual cell so as to minimize the total communication cost for the global mobile network where inter-virtual cell communication is more expensive than intra-virtual cell communication (K. Lim and Y.-H. Lee, IEEE Personal, Indoor and Mobile Radio Communications PIMRC'94, pp. 1237-1241, Sep. 1994; K. Lim, Y.-H. Lim and Y.-H. Lee, IEEE ICC'95, pp. 1839-1843, June 1995). To demonstrate the correct operations of VCP and measure data which are used as parameters to a performance model for the virtual cell system, we implement VCP on a simulated environment. The performance analysis of the virtual cell system is out of scope in this paper and one is referred to K. Lim, Y.-H. Lim and Y.-H. Lee, Proc. 10th Int. Conf. Information Networking ICOIN-10, pp. 551-560, Jan. 1996.
2908844
Operation-based Update Propagation in a Mobile File System
In this paper we describe a technique called operation-based update propagation for efficiently transmitting updates to large files that have been modified on a weakly connected client of a distributed file system. In this technique, modifications are captured above the file-system layer at the client, shipped to a surrogate client that is strongly connected to a server, re-executed at the surrogate, and the resulting files transmitted from the surrogate to the server. If re-execution fails to produce a file identical to the original, the system falls back to shipping the file from the client over the slow network. We have implemented a prototype of this mechanism in the Coda File System on Linux, and demonstrated performance improvements ranging from 40 percents to nearly three orders of magnitude in reduced network traffic and elapsed time. We also found a novel use of forward error correction in this context.
45657020
Partial convexification cuts for 0-1 mixed-integer programs
Abstract In this research, we propose a new cut generation scheme based on constructing a partial convex hull representation for a given 0–1 mixed-integer programming problem by using the reformulation–linearization technique (RLT). We derive a separation problem that projects the extended space of the RLT formulation into the original space, in order to generate a cut that deletes a current fractional solution. Naturally, the success of such a partial convexification based cutting plane scheme depends on the process used to tradeoff the strength of the cut derived and the effort expended. Accordingly, we investigate several variable selection rules for performing this convexification, along with restricted versions of the accompanying separation problems, so as to be able to derive strong cuts within a reasonable effort. We also develop a strengthening procedure that enhances the generated cut by considering the binariness of the remaining unselected 0–1 variables. Finally, we present some promising computational results that provide insights into implementing the proposed cutting plane methodology.
17849984
Analysis of Backward Error Recovery for Concurrent Processes with Recovery Blocks
Although backward error recovery with recovery blocks (RPs) has received considerable attention from many researchers, no attempt has been made to structure its implementation alternatives and then to evaluate/analyze their effectiveness. The authors categorize three different methods of implementing RBs. These are the asynchronous, synchronous, and the pseudo recovery point (prp) implementations. The authors have developed probabilistic models for estimating (I) the interval between two successive recovery lines for asynchronous RBs, (II) mean loss in computation power for the synchronous method, and (III) additional overhead and rollback distance in the case when PRPs are used. 11 references.