2382569
Filtering XPath expressions for XML access control
XPath is a standard for specifying parts of XML documents and a suitable language for both query processing and access control of XML. In this paper, we use the XPath expression for representing user queries and access control for XML. And we propose an access-control method for XML, where we control accesses to XML documents by filtering query XPath expressions through access-control XPath expressions. For filtering the access-denied parts out of query XPath expressions, set operations (such as, intersection and difference) between the XPath expressions are essential. However, it is known that the containment problem of two XPath expressions is coNP-hard when the XPath expressions contain predicates (or branch), wildcards and descendant axes. To solve the problem, we directly search XACT (XML Access Control Tree) for a query XPath expression and extract the access-granted parts. The XACT is our proposed structure, where the edges are structural summary of XML elements and the nodes contain access-control information. We show that the query XPath expressions are successfully filtered through the XACT by our proposed method, and also show the performance improvement by comparing the proposed method with the previous work.
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
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.
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.
46434197
Flow Control Strategy for Flexible Machining and Assembly System
Abstract In this paper an effective flow control strategy for a Flexible Machining and Assembly System is proposed using the concepts of operation-oriented and, combined push and pull control method. The proposed flow control mechanism could meet production demands with a minimum makespan while satisfying assigned due-dates and keeping a low volume of work-in-process at the same time. It also considers machine failures and rush jobs.
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.
1051446
Integrated scheduling with garbage collection for real-time embedded applications in CLI
We present a schedulable garbage collection for realtime applications in virtual machine environments. The design objective is to make the pause time caused by garbage collection operations controllable, and the invocation of garbage collection predictable. Thus, real-time applications can be schedulable along with garbage collection. We develop a prototype for a schedulable garbage collection in MONO CLI execution environment. A cost model of garbage collection is established based on measured WCET to predict the execution time and overhead of garbage collection operations. A scheduling algorithm of garbage collection and application tasks is presented to illustrate how the time and memory constraints of real-time systems can be met. The experiment result of the scheduling algorithm for a periodic task set on the prototype is included in the paper
207563187
Data quality assessment
How good is a company's data quality? Answering this question requires usable data quality metrics. Currently, most data quality measures are developed on an ad hoc basis to solve specific problems [6, 8], and fundamental principles necessary for developing usable metrics in practice are lacking. In this article, we describe principles that can help organizations develop usable data quality metrics.
19081367
Robust technique for estimating the bearings of cyclostationary signals
This paper deals with the problem of direction finding using cyclostationary signals in the presence of cycle frequency error (CFE). By exploiting the signal cyclostationarity, cyclic MUSIC and conjugate cyclic MUSIC presented in Gardner (Cyclostationarity in Communications and Signal Processing, New York, 1994; Proc. IEEE 76 (1988) 845) have been shown to be effective for signal-selective direction finding. However, they suffer from severe performance degradation even if there is a small error in the cycle frequency of the signals of interest. In this paper, we first evaluate the performance of conjugate cyclic MUSIC when CFE exists. An analytical formula is derived to show the behavior of the performance degradation due to CFE. By exploiting the eigenstructure of the conjugate cyclic correlation matrix of the received array data, we develop a technique including a method for estimating the cycle frequency of the SOI and an efficient method in conjunction with a subspace-fitting algorithm to achieve robust direction finding against CFE. Several simulation examples confirming the theoretical analysis and showing the effectiveness of the proposed technique are also presented.