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
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.
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.
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.
2918771
DiSigncryption: an integration of agent-based signature delegation with distributed reputation management scheme
This paper presents a distributed signcryption with verifiable partial signature (DiSigncryption) protocol that allows a mobile agent owner, participating in e-commerce transaction, to securely delegate and distribute his/her signing capability among a set of trusted third party hosts (TTP-hosts) via a mobile agent. The protocol incorporates three schemes: a novel distributed reputation management scheme, a modified version of the distributed signcryption method proposed in [Y. Mu et al., (2000)], and the agent-based threshold proxy signcryption (ATPS) protocol proposed in [O. Bamasak et al., (2004)]. The most notable feature of the DiSigncryption protocol is that, in addition to allowing secure distributed proxy signature generation, it enables the agent owner to quantitatively assess the trust and reliability of each of the TTP-hosts that s/he has dealt with. These trust and reliability values are then aggregated into an index to guide the agent owner in making his/her decision as which TTP-hosts should be used in his/her next dealing. The security properties of the proposed protocol are analyzed, and the protocol is compared with the most related work.
18850818
A Fast Algorithm for the Chirp Rate Estimation
A fast algorithm for the chirp rate estimation is presented in this paper. By the computation of the cubic phase transform (CPT) of the signal, it is shown that the CPT is concentrated along the frequency rate law of the signal, and the peak of the CPT yields the estimate of the chirp rate. The proposed algorithm is fast in that it requires only one-dimensional (1-D) maximizations. The asymptotic statistical result is derived for the chirp rate estimation, and the computer simulation demonstrates that, when the input signal-to-noise ratio (SNR) is higher than -2 dB, the simulation results and the theoretical analyses are well matched, and the mean-square error (MSE) approaches optimality as the SNR tends to infinity.
13934101
E-learning and Its Information Technology
E-learning will be introduced as an integral part of an environment where teaching is transformed and where learning is an ongoing, creative process. In this paper, we discuss the e-learning and its technology. Our world is changing, and information and communication technology (ICT) is central to this change. Digital media has revolutionized the information society. These advances in ICT have dramatically changed the learning and teaching process, and have expanded new learning opportunities and access to educational resources beyond those traditionally available. ICT, when successfully integrated into teaching and learning, can ensure the meaningful interaction of learners with information.
32437026
Fuzzy Comprehensive Evaluation for Power Network Operating Schemes
Based on the analytic hierarchy process, a fuzzy comprehensive evaluation method is proposed for power network operating schemes. Performance indices and corresponding membership functions are presented to denote their contributions on overall objective. The analytic hierarchy process is used to analyze influencing factors, to establish a hierarchical model and to rank the influencing factors in order of importance. After detailed analyses and calculations for each operating scheme, quantitative evaluation results that considering various factors comprehensively are obtained by a two-level fuzzy comprehensive evaluation. A decision support system using the proposed method is developed. Simulation results of a practical power system show its validity and effectiveness.
8279850
Analysis and Simulation Protocols Based on Slotted ALOHA for Plastic Optical Fiber Network
In this paper a novel multipriority reservation protocols for plastic optical fiber network is proposed. In conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels which be restricted by BER. To resolve this problem, a novel protocol based on slotted ALOHA is proposed in this paper. By using the reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict can be avoided. The protocol can efficiently support the transmission of multimedia messages that require the different time-delay. The network throughput and average delay has been investigated by numerical analysis and simulation experiments. It is showed that the multipriority reservation protocol in this POF network is valid and efficient.