598542
XSEED: Accurate and Fast Cardinality Estimation for XPath Queries
We propose XSEED, a synopsis of path queries for cardinality estimation that is accurate, robust, efficient, and adaptive to memory budgets. XSEED starts from a very small kernel, and then incrementally updates information of the synopsis. With such an incremental construction, a synopsis structure can be dynamically configured to accommodate different memory budgets. Cardinality estimation based on XSEED can be performed very efficiently and accurately. Extensive experiments on both synthetic and real data sets show that even with less memory, XSEED could achieve accuracy that is an order of magnitude better than that of other synopsis structures. The cardinality estimation time is under 2% of the actual querying time for a wide range of queries in all test cases.
11505780
InterJoin: Exploiting Indexes and Materialized Views in XPath Evaluation
XML has become the standard for data exchange for a wide variety of applications, particularly in the scientific community. In order to efficiently process queries on XML representations of scientific data, we require specialized techniques for evaluating XPath expressions. Exploiting materialized views in query processing significantly enhances query processing performance. We propose a novel view definition that allows for intermediate (structural) join results to be stored and reused in XML query evaluation. Unlike current XML view proposals, our views do not require navigation in the original document or path-based pattern matching. Hence, they are evaluated significantly faster and are easily costed as part of a query plan. In general, current structural joins cannot exploit views efficiently when the view definition is not a prefix (or a suffix) of the XPath query. To increase the applicability of our proposed view definition, we propose a novel physical structural join operator called InterJoin. The InterJoin operator allows for joining interleaving XPath expressions, e.g., joining //A//C with //B to evaluate //A//B//C. InterJoin allows for more join alternatives in XML query plans. We propose several physical implementations for InterJoin, including a technique to exploit spatial indexes on the inputs. We give analytic cost models for the implementations so they can be costed in an existing XML query optimizer. Experiments on real and synthetic XML data show significant speed-ups of up to 200% using InterJoin, and speed-ups of up to 400% using our materialized views
9362943
Finding shortest paths in large network systems
This paper describes a disk-based algorithm for finding shortest paths in a large network system. It employs a strategy of processing the network piece by piece and is based on new algorithms for graph partitioning and for finding shortest paths that overcome the problem of existing approaches. To show that it is scalable to large network systems and is adaptable to different computing environments, seven states in Tiger/Line files are extracted as test cases and are experimented on machines with different configurations. The running time for finding the shortest path depends primarily on the power of the underlying systems. Moreover, to run the algorithm optimally, the memory requirement is not large, even for a very large network system such as the road system in several states in Tiger/Line file. To evaluate its performance, New Mexico state road system is used as the test case, and is compared with Dijkstra's algorithm. The average running time of the proposed algorithm is, in the worst case, about two and a half times slower than that of Dijkstra's algorithm; provided that in Dijkstra's algorithm, the whole graph can be fit into main memory and is already loaded in advance. If the I/O time for loading the whole graph is counted, the proposed algorithm is faster in essentially all cases.
10807744
XML Query Processing and Optimization
In this paper, I summarize my research on optimizing XML queries This work has two components: the first component is the definition of a logical algebra and logical optimization techniques This algebra can be translated into different physical algebras such as native or extended-relational algebras The second component is the design of physical storage structures and physical optimization techniques.
35884730
Compact access control labeling for efficient secure XML query evaluation
Fine-grained access controls for XML define access privileges at the granularity of individual XML nodes. In this paper, we present a fine-grained access control mechanism for XML data. This mechanism exploits the structural locality of access rights as well as correlations among the access rights of different users to produce a compact physical encoding of the access control data. This encoding can be constructed using a single pass over a labeled XML database. It is block-oriented and suitable for use in secondary storage. We show how this access control mechanism can be integrated with a next-of-kin (NoK) XML query processor to provide efficient, secure query evaluation. The key idea is that the structural information of the nodes and their encoded access controls are stored together, allowing the access privileges to be checked efficiently. Our evaluation shows that the access control mechanism introduces little overhead into the query evaluation process.
5525123
FIX: feature-based indexing technique for XML documents
Indexing large XML databases is crucial for efficient evaluation of XML twig queries. In this paper, we propose a feature-based indexing technique, called FIX, based on spectral graph theory. The basic idea is that for each twig pattern in a collection of XML documents, we calculate a vector of features based on its structural properties. These features are used as keys for the patterns and stored in a B+tree. Given an XPath query, its feature vector is first calculated and looked up in the index. Then a further refinement phase is performed to fetch the final results. We experimentally study the indexing technique over both synthetic and real data sets. Our experiments show that FIX provides great pruning power and could gain an order of magnitude performance improvement for many XPath queries over existing evaluation techniques.
26443511
Revocation invocation for accountable anonymous PKI certificate trees
Anonymous accountable PKI certificates are a form of unlinkable credential and have been proposed for several on-line applications where the holder of the certificate requires anonymity in terms of identity, location and history. One of the current deficiencies with anonymous accountable certificates is the lack of appropriate revocation mechanisms. Since revocation is part of key management, this deficiency is one impediment to the commercial adoption of anonymous accountable PKI certificates. This paper presents a revocation scheme for an anonymous accountable PKI certificate tree.
37809849
Sixty-phase generalized Barker sequences
The extension of the list of known generalized Barker sequences to length 19 is proposed. Examples for all lengths up to 19 where the terms of the sequence are sixtieth roots of unity are given. >
5798533
A Flexible Routing Decision Framework to Support Diversified Application-Level Data Types in MANETs
Owing to the technological advances in computing power and wireless communications, applications that used to be only accessible on desktop computers are increasingly run-able on wireless devices. As a result, a wireless device user may run several applications at the same time, and these different applications may generate different data types. In a mobile ad hoc network (MANET) environment, which is popular among wireless device users, different data types may impose different routing considerations and prefer using different routing criteria. To support diversified routing requirements and to achieve efficient routing for applications with different data types, this paper proposes a novel Flexible Routing Decision (FRD) framework. The framework supports several routing metric types in one platform. It allows users to weigh, rank and use different types of routing metrics to select different routes on an individual application basis. It is expected that this approach could help users to find a route that is most suited to their application requirements.
15131459
An Ant Colony Optimization Algorithm for Learning Classification Rules
Ant colony optimization (ACO) algorithm has been applied to data mining recently. Aiming at Ant Miner, a classification rule learning algorithm based on ACO, this paper presents an enhanced Ant Miner, which includes two main contributions. Firstly, a rule punishing operator is employed to reduce the number of rules and the number of conditions. Secondly, an adaptive state transition rule and a mutation operator are applied to the algorithm to speed up the convergence rate. The results of experiments on some data sets demonstrate that the enhanced Ant-Miner can quickly discover better classification rules which have roughly competitive predicative accuracy and short rules
17772901
Interference Temperature Estimation Based on the Detection and Estimation of Angles of Arrival of Multiple Wide-Band Sources in Cognitive Radio Sensor Networks
Majority of evaluation methods on interference temperature algorithms are based on the assumption that either the interference signals or the user’s signals are no directions. This is a mathematical constraint that is not satisfied in many applications. In fact, without consideration the signal directions increase estimation interference temperature, that is, reduce the frequency utilizing chance for users. In this paper, we consider situations where the interference signals and user’s signals have directions in cognitive radio sensor networks. We propose an algorithm that estimates the interference temperature of this model using a generalization of the DOA¿direction of arrival algorithm. From this, we find the interference temperature and show that it does become smaller. We compare our method to the conventional (without considering directions) algorithm. The simulation studies show that the new method outperforms the conventional algorithm by reducing the estimation interference temperature and improving the frequency spectrum efficiency.