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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Nikolay Borissov Dirk Neumann Christof Weinhardt 《Autonomous Agents and Multi-Agent Systems》2010,21(2):115-142
Autonomous agents are widely applied to automate interactions in robotics, e.g. for selling and purchasing goods on eBay,
and in financial markets, e.g. in the form of quote machines and algorithmic traders. Current research investigates efficient
economic mechanisms that fully automate the provisioning and usage processes of Grid-based services. On the one hand, consumers
want to allocate resources on demand for their various applications, e.g. data sharing, stream processing, email, business
applications and simulations. On the other hand, providers of Grid services want to govern business policies to meet their
utilization and profit goals. The above-mentioned processes are not manually manageable, however, because decisions need to
be taken within milliseconds. Therefore, such processes have to be automated to minimize human interactions. Hence, market
mechanisms and strategic behavior play important roles when it comes to achieving automated and efficient allocation of Grid
services. The paper begins by presenting a framework for automated bidding, providing a methodology for the design and implementation
of configurable bidding strategies. Second, it presents a novel bidding strategy based on a reinforcement learning technique.
This strategy is designed to automate the bid generation processes of consumers and providers in various market mechanisms.
Third, the behavior and convergence of the strategy is evaluated in a centralized Continuous Double Auction and a decentralized
on-line machine scheduling mechanism against selected benchmark bidding strategies. Fourth, we define a bidding language for
communicating consumer and provider preferences to the market as well as report back the match of the market-based allocation
process. 相似文献
992.
XMin: Minimizing Tree Pattern Queries with Minimality Guarantee 总被引:1,自引:0,他引:1
Due to wide use of XPath, the problem of efficiently processing XPath queries has recently received a lot of attention. In
particular, a considerable effort has been devoted to minimizing XPath queries since the efficiency of query processing greatly
depends on the size of the query. Research work in this area can be classified into two categories: constraint-independent
minimization and constraint-dependent minimization. The former minimizes queries in the absence of integrity constraints while
the latter in the presence of them. For a linear path query, which is an XPath query without branching predicates, existing constraint-independent minimization methods are generally
known to be unable to minimize the query without processing the query itself. Most recently, however, by using the DataGuide, a representative structural summary of XML data, a constraint-independent method that minimizes linear path queries in a
top-down fashion has been proposed. Nevertheless, this method can fail to find a minimal query since it minimizes a query
by merely erasing labels from the original query whereas a minimal query could include labels that are not present in the
original query. In this paper, we propose a bottom-up approach called XMin that guarantees finding a minimal query for a given tree pattern query by using the DataGuide without processing the query itself. For the
linear path query, we first show that the sequence of labels occurring in the minimal query is a subsequence of every schema label sequence that matches the original query. Here, the schema label sequence for a node is the sequence of labels from the root of XML
data to the node. We then propose iterative subsequence generation that iteratively generates subsequences from the shortest schema label sequence matching the original query in a bottom-up
fashion and tests query equivalence. Using iterative subsequence generation, we can always find a minimal query and we formally
prove this guarantee. We also propose an extended algorithm that guarantees the minimality for the tree pattern query, which is a linear path query with branching predicates. These methods have been prototyped in a full-fledged object-relational
DBMS. The experimental results using real and synthetic data sets show the practicality of our method. 相似文献
993.
Xiaoying Wu Dimitri Theodoratos Stefanos Souldatos Theodore Dalamagas Timos Sellis 《World Wide Web》2010,13(4):441-474
Finding the occurrences of structural patterns in XML data is a key operation in XML query processing. Existing algorithms
for this operation focus almost exclusively on path patterns or tree patterns. Current applications of XML require querying
of data whose structure is complex or is not fully known to the user, or integrating XML data sources with different structures.
These applications have motivated recently the introduction of query languages that allow a partial specification of path
patterns in a query. In this paper, we consider partial path queries, a generalization of path pattern queries, and we focus
on their efficient evaluation under the indexed streaming evaluation model. Our approach explicitly deals with repeated labels
(that is, multiple occurrences of the same label in a query). We show that partial path queries can be represented as rooted
dags for which a topological ordering of the nodes exists. We present three algorithms for the efficient evaluation of these
queries. The first one exploits a structural summary of data to generate a set of path patterns that together are equivalent
to a partial path query. To evaluate these path patterns, we extend a previous algorithm for path-pattern queries so that
it can work on path patterns with repeated labels. The second one extracts a spanning tree from the query dag, uses a stack-based
algorithm to find the matches of the root-to-leaf paths in the tree, and merge-joins the matches to compute the answer. Finally,
the third one exploits multiple pointers of stack entries and a topological ordering of the query dag to apply a stack-based
holistic technique. We analyze our algorithms and perform extensive experimental evaluations. Our experimental results show
that the holistic algorithm outperforms the other ones. Our approaches are the first ones to efficiently evaluate this class
of queries in the indexed streaming model. 相似文献
994.
An approach for moving object recognition based on BPR and CI 总被引:1,自引:0,他引:1
A recognition and classification method of multiple moving objects in traffic based on the combination of the Biomimetic Pattern
Recognition (BPR) and Choquet Integral (CI) is proposed. The recognition process consists of three stages. At the first stage,
vehicles and pedestrians are detected in video images and the area, the shape and the velocity features are obtained by classical
methods. At the second stage, BPR is used to classify the Zernike moments extracted at the first stage. At the last stage,
CI is then adopted for multi-features fusion based on the output of BPR, and the area and the velocity features obtained at
the first stage to improve the recognition accuracy. Experiment results show that this approach is efficient. 相似文献
995.
One of congress’ goals for 2007 was for 80% of all tax and informational returns to be filed electronically. However, to date
that lofty goal has fallen well short. This research proposes a model of e-filing adoption. To test the model a survey is
administered to 260 participants. The instrument assesses citizen perceptions of trust, risk and optimism bias. Structural
equation modeling is used to evaluate the relationships between these three concepts and intention to use. The results indicate
that trust of the Internet, trust of the e-filer, perceived risk and optimism bias all have an impact on intention to use
e-filing. Implications for practice and research are discussed. 相似文献
996.
997.
998.
Making changes to software systems can prove costly and it remains a challenge to understand the factors that affect the costs
of software evolution. This study sought to identify such factors by investigating the effort expended by developers to perform
336 change tasks in two different software organizations. We quantitatively analyzed data from version control systems and
change trackers to identify factors that correlated with change effort. In-depth interviews with the developers about a subset
of the change tasks further refined the analysis. Two central quantitative results found that dispersion of changed code and
volatility of the requirements for the change task correlated with change effort. The analysis of the qualitative interviews
pointed to two important, underlying cost drivers: Difficulties in comprehending dispersed code and difficulties in anticipating
side effects of changes. This study demonstrates a novel method for combining qualitative and quantitative analysis to assess
cost drivers of software evolution. Given our findings, we propose improvements to practices and development tools to manage
and reduce the costs. 相似文献
999.
We consider Constraint Satisfaction Problems in which constraints can be initially incomplete, where it is unknown whether
certain tuples satisfy the constraint or not. We assume that we can determine the satisfaction of such an unknown tuple, i.e.,
find out whether this tuple is in the constraint or not, but doing so incurs a known cost, which may vary between tuples.
We also assume that we know the probability of an unknown tuple satisfying a constraint. We define algorithms for this problem,
based on backtracking search. Specifically, we consider a simple iterative algorithm based on a cost limit on the unknowns
that may be determined, and a more complex algorithm that delays determining an unknown in order to estimate better whether
doing so is worthwhile. We show experimentally that the more sophisticated algorithms can greatly reduce the average cost. 相似文献